the people have bee masters of their country science can really serve the people.
A. It is only then; that
B. It was that; when
C. It is only when; that
D. It was when; then
网友回答
A. It is only then; that
B. It was that; when
(答案→)C. It is only when; that
D. It was when; then
解析：本题考查强调句型。被强调部分为状语从句only when the people...country；that为强调句型的引导词。