Alkyl halides are considered to be very reactive compounds towards nucleophile because_________________?

Alkyl halides are considered to be very reactive compounds towards nucleophile because_________________?

A. they have an electrophilic carbon
B. they have an electrophilic carbon & a good leaving group
C. they have an electrophilic carbon & a bad leaving group
D. they have a nucleophilic carbon & a good leaving group