The regular expression R=a*b(ab)*c(abc)* decides the subset of {a,b,c}* of strings in which (mark the one description below that describes exactly the strings accepted by R)

A. at least one b and at least one c appear.

B. b and c both appear, and the first b appears before the first c.

C. every appearance of b is followed eventually by a c.

D. the substring bc appears