题目内容
21、The scientist's discoveries were of great help to mankind．
A．a；the B．a；／ C．／；／ D．the；the
试题答案
21、C
The scientist's discoveries were of great help to mankind．
The scientist's discoveries were of ____________great help to ____________mankind．
A．a；the B．a；／ C．the；the D．／；／