The correct option is (b) 2
Easy explanation: There are a total of 2 properties associated with the Response event namely:
PerformanceTiming.responseEnd
PerformanceTiming.responseStart.
PerformanceTiming.responseStart read-only property returns an unsigned long long representing the moment in time (in milliseconds since the UNIX epoch) when the browser received the first byte of the response from the server, cache, or local resource.