Explanation
Juniper ATP Cloud is a cloud-based threat detection service that protects all hosts in your network against evolving security threats. Juniper ATP Cloud performs the following tasks:
It extracts potentially malicious objects and files from the traffic and sends them to the cloud for analysis.
It uses multiple antivirus software packages to analyze files and identify known malicious files quickly.
It also uses other techniques, such as machine learning, sandboxing, and behavioral analysis, to identify new malware and add it to the known list of malware.
It correlates between newly identified malware and known command and control (C&C) sites to aid analysis.
It blocks known malicious file downloads and outbound C&C traffic.
It provides features such as DNS, Encrypted Traffic Insights (ETI) and IoT security if you have ATP Cloud premium license.
Based on this information, we can infer the following:
Option B is correct because Juniper ATP Cloud uses multiple antivirus software packages to analyze files, as well as other techniques, to provide robust coverage against sophisticated, evasive threats.
Option D is correct because Juniper ATP Cloud does not use antivirus software packages to protect against zero-day threats, which are unknown and undetected by traditional antivirus solutions. Instead, it uses other techniques, such as machine learning, sandboxing, and behavioral analysis, to identify and mitigate zero-day threats.
Option A is incorrect because Juniper ATP Cloud does not only use one antivirus software package to analyze files, but multiple ones, as well as other techniques.
Option C is incorrect because Juniper ATP Cloud does not use antivirus software packages to protect against zero-day threats, but other techniques.
References: Juniper Security, Specialist (JNCIS-SEC) Reference Materials and Juniper Security, Professional (JNCIP-SEC) Reference Materials
https://blogs.juniper.net/en-us/security/juniper-strengthens-connected-security-portfolio-with-new-risk-based-acc
https://blogs.juniper.net/en-us/security/juniper-strengthens-connected-security-portfolio-with-new-risk-based-acc

AppTrack is a feature of Juniper Networks firewall solutions that allows administrators to track applications, users, and the amount of traffic generated by those applications on the network. AppTrack can be enabled on specific security zones of the network to monitor traffic on those zones. This feature can be used to determine how much traffic a popular gaming application is generating on the network. For more information, please refer to the Juniper Networks JNCIS-SEC Study Guide.
Reference:
AppTrack is a feature of the Junos OS that provides visibility into the applications and users on your network. It tracks the usage of applications and provides detailed reports on the amount of traffic generated by each application. By enabling AppTrack on the proper security zones, you can determine how much traffic a popular gaming application is generating on your network.