_________ the right kind of training, these teenage soccer players may one day grow into the international stars.

A．Giving

B．Having given

C．To give

D．Given

烷烃是由某单烯烃与H₂加成后的产物，若不考虑烯烃的顺反异构，则这种单烯烃的结构可能有（　　）

A．4种

B．5种

C．6种

D．7种