Some people return to college a...

Câu hỏi: Some people return to college as mature students and take full- or part-time training courses in a skill will help them to get a job. The development of open learning, (26)______ it possible to study when it is convenient for the students, has increased the opportunities available (27)_______ many people. This type of study was formerly restricted to book-based learning and (28)________ course but now includes courses on TV, CD-ROM or the Internet, and self-access courses at language or computer centers.

A. about

B. with 

C. to

D. by