802.11b (Wi-Fi 1)
11 Mbps
100 meter maximum effective range
802.11a (Wi-Fi 2)
54 Mbps
50 meter maximum effective range

Physical security is the protection of the physical assets and resources of an organization from unauthorized access, damage, or theft1.
Physical security detection devices are devices that can monitor and alert on the presence or activity of intruders, unauthorized personnel, or environmental hazards in a physical location12.
Cameras are examples of physical security detection devices, as they can capture and record video footage of the surroundings, and send alerts or notifications to the security personnel or the network administrator12.
Cameras can also act as a deterrent for potential intruders, as they can make them aware that they are being watched and recorded2.
The other options are not considered physical security detection devices, as they have different functions or purposes, such as:
Biometric readers are devices that can authenticate the identity of a person based on their unique biological characteristics, such as fingerprints, iris scans, or facial recognition12. Biometric readers are examples of physical security prevention devices, as they can prevent unauthorized access to a physical location or a device2.
Access control vestibules are structures that can control the entry and exit of people or vehicles to a physical location, such as a building, a room, or a parking lot13. Access control vestibules are examples of physical security containment devices, as they can contain or isolate a physical location or a device3.
Locking racks are devices that can secure the physical components of a network device, such as a server, a router, or a switch, inside a metal enclosure or a cabinet1 . Locking racks are examples of physical security protection devices, as they can protect a physical device from damage, theft, or tampering. Reference:
1: CompTIA Network+ N10-008 Cert Guide, 1st Edition, Chapter 14: Network Security, pp. 566-569
2: CompTIA Network+ N10-008 Cert Guide, 1st Edition, Chapter 14: Network Security, p. 570
3: Access Control Vestibule - Wikipedia
4: CompTIA Network+ N10-008 Cert Guide, 1st Edition, Chapter 2: Network Devices, p. 67

A door lock would be the best security device to use to provide mechanical access control to the MDF/IDF. A door lock is a device that prevents unauthorized access to a physical area by requiring a key, a code, a card, a biometric scan, or a combination of these factors to open it. A door lock can provide mechanical access control to the MDF/IDF, which are rooms that house network equipment such as switches, routers, servers, or patch panels. A door lock can prevent unauthorized persons from tampering with or stealing the network equipment or data. Reference: https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Data_Center/DC_Infra2_5/DCInfra_6.html

iperf is a tool that can measure the bandwidth and quality of a network link by generating and transferring TCP or UDP data streams. iperf can report the maximum achievable throughput, packet loss, jitter, and other statistics for a given link. iperf can be used to test both the uplink and downlink performance of a network link by running it on two endpoints and specifying the direction and duration of the test. iperf can help the engineer verify that the new fiber uplink meets the throughput requirements for the office network.
tcpdump is a tool that can capture and analyze network traffic by filtering and displaying packets based on various criteria. tcpdump can help the engineer troubleshoot network problems, monitor network activity, and inspect packet contents, but it cannot measure the throughput or quality of a network link.
ping is a tool that can test the reachability and latency of a network host by sending and receiving ICMP echo packets. ping can help the engineer check if the new fiber uplink is connected and responsive, and how long it takes for packets to travel between the endpoints, but it cannot measure the throughput or quality of a network link.
netstat is a tool that can display information about the network connections, routing tables, interfaces, and protocols on a network host. netstat can help the engineer view the status and details of the network connections using the new fiber uplink, but it cannot measure the throughput or quality of a network link.
Reference
iperf - The ultimate speed test tool for TCP, UDP and SCTP
How to use iperf to test local network LAN speed in Windows 10
How to Test Network Performance Between Two Linux Servers
What is tcpdump?
8 Common Network Utilities Explained
Monitoring Your Network: ping, netstat, tcpdump, and Ethereal
Netstat vs. Nmap vs. Netcat: Understanding the Differences

The difference between piggybacking and tailgaiting is that with piggybacking, the person is willfully and intentionally letting you in. In this particular case, the person caught the door before it closed, so it is tailgating.
Tailgating is a physical security attack that occurs when an unauthorized person follows an authorized person through a secured door or gate without their knowledge or consent. Tailgating can allow an attacker to bypass access control mechanisms and gain entry to restricted areas or resources. Tailgating can also pose a safety risk for the authorized person and other occupants of the facility.
Piggybacking is a physical security attack that occurs when an unauthorized person follows an authorized person through a secured door or gate with their knowledge or consent. Piggybacking can also allow an attacker to bypass access control mechanisms and gain entry to restricted areas or resources. Piggybacking can also violate security policies and compromise the accountability of the authorized person.
Shoulder surfing is a physical security attack that occurs when an unauthorized person observes or records an authorized person's confidential information, such as passwords, PINs, or credit card numbers. Shoulder surfing can allow an attacker to steal credentials and access sensitive data or systems. Shoulder surfing can also violate privacy and confidentiality rights of the authorized person.
Phishing is a cyber security attack that occurs when an unauthorized person sends fraudulent emails or messages that appear to come from legitimate sources, such as banks, companies, or government agencies. Phishing can trick recipients into clicking on malicious links, opening malicious attachments, or providing personal or financial information. Phishing can allow an attacker to install malware, steal credentials, or perform identity theft. Phishing does not involve physical access to secured doors or gates.