When he suddenly ________ up the subject of genetic engineering, there was an embarrassedsilence.
The director recommended that she ________ (study) more English before going abroad.
過渡時期的總路線的主體是 ________。
中國共產黨在過渡時期總路線的主體是 ___________。
1953 年，為解決糧食供應緊張問題，我國采取的新措施是 ()
上具有連續導數，則()