2.30.

A. 　 if

B. 　 after

C. 　 that

D. 　 though

A. 　 reusing

B. 　 reused

C. 　 reuses

D. 　 to be reused

A. 　 as to be heard

B. 　 to be heard

C. 　 as to hear

D. 　 to hear

A. 　because

B. 　 where

C. 　 once

D. 　 although

A. 　 the others

B. 　 another

C. 　 others

D. 　 the other

A. 　 having cried

B. 　 cry

C. 　 to cry

D. 　 crying