You support an application running on App Engine. The application is used globally and accessed from various device types. You want to know the number of connections. You are using Stackdriver Monitoring for App Engine. What metric should you use? 

Answer options:

A. flex/connections/current
B. tcp_ssl_proxy/new_connections
C. tcp_ssl_proxy/open_connections
D. flex/instance/connections/current

D

Reference: https://cloud.google.com/monitoring/api/metrics_gcp