The American alligator population in the Florida Everglades has decreased by three percent since October, when careful

[BTGmoderatorDC]

The American alligator population in the Florida Everglades has decreased by three percent since October, when careful enumeration started.

A) since October, when careful enumeration started
B) since October, at which time the careful enumeration started
C) from October, the start of careful enumeration
D) from October, which was the start of careful enumeration
E) after October, when the careful enumeration started


OA A

Source: Princeton Review

[Rk4]

"When" is used to refer to a particular time. Here we are referring to 'October' so when is the correct usage