In English, [l] and [ɫ] are allophones of the phoneme /l/ because they occur in ___________________, i.e., they never appear in the same sound contexts. [l] always occurs before vowels (as in the word leaf, look), while [ɫ] comes after vowels and before consonants (as in the word feel, cold).
A、free variation
B、 a minimal set
 
C、complementary distribution
D、regional differences