We forgave his bad temper because we knew that his son's illness had put him under great _____. A. emotion B. excitement C. crisis D. stress 答案: D.考查动词短语的构成。 put sb. under(great) stress使某人处境(非常)紧张,使某人受(很大)压力。 有关基因重组的说法,不正确的是( )
A.基因重组是生物变异的根本来源 B.基因重组不一定能产生新的性状
C.基因重组一般发生在有性生殖过程中 D.非同源染色体上的非等位基因可以发生重组