Which of the following choices is best suited for this requirement?

Karl wants to define a character class that includes any alphanumeric word characters.
Which of the following choices is best suited for this requirement?

A.
/[a-zA-Z_0-9]/;

B.
/^w/;

C.
/[^a-zA-Z_0-9]/;

D.
/[^0-Z$]/;