What piece of code would you use to obtain an array of response headers for a given URL, indexed by

What piece of code would you use to obtain an array of response headers for a given URL,
indexed by their respective names?

A.
get_headers($url);

B.
get_header($url);

C.
stream_context_get_headers($url);

D.
get_headers($url, 1);

E.
get_headers($url, ASSOC_HEADERS);