（ ）courses enable students to extend their studies in other areas so as to widen their knowledge. (option)
A.正确答案DOption
B.Options
C.Optionally
D.Optional
（ ）courses enable students to extend their studies in other areas so as to widen their knowledge. (option)
（ ）courses enable students to extend their studies in other areas so as to widen their knowledge. (option)
A.正确答案DOption
B.Options
C.Optionally
D.Optional
