The impact of adding more SSIDs to a radio is beacon overhead.So,the correct answer is A.beacon overhead

Basic data rates are the required data rates that all devices on a wireless network must support in order to connect to the network. These rates are used for management and control frames and can affect the performance of the network.
According to the Lecture 3 - Radio Frequency and Antenna Fundamentals - Part 2 document2, basic data rates are required data rates that all devices must support to communicate on a WLAN.

The 37% of Successful Connects suggest that 63% failed - however, these are spread between both LD_Testbed_MD and LD_RS_Support. If the only AP with connection issues was LD_RS_Support then the reverse math may have worked.

In this scenario, you would begin troubleshooting by checking the WLAN-level Pre-Shared Keys.
According to the Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide1, you can configure a time-based setting for WLAN-level Pre-Shared Keys (PSKs) that will reset the key after a specified interval. This feature is useful for enhancing security and preventing unauthorized access. If a user reports that the Wi-Fi worked for a week and now it does not work, you should check the WLAN-level PSK settings and see if the key has been changed.