The United Nations Conference on Global Environment, which took place earlier this year in Vienna, was a very（） meeting.

A.productive

B.communicative

C.aggressive

D.protective

改革开放30年来，我国社会最鲜明的特点是（）。

A．改革开放

B．与时俱进

C．解放思想

D．坚持社会主义道路