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举一反三
【单选题】In the 1920s demand for American farm products fell, as European countries began to recover from World War I and instituted austerity (紧缩) programs to reduce their imports. The result was a sharp drop...
A.
might cause greater scarcity of farm products
B.
didn't give the Secretary of Agriculture enough power
C.
would benefit neither the government nor the farmers
D.
benefited one group of citizens at the expense of others
【单选题】当F+×F-杂交是下列说法对的是( )
A.
F因子几乎总不转移到F+细胞中
B.
F- 菌株几乎总成为F+
C.
基因重组的发生频率较高
D.
F因子经常插入到F-细胞染色体上
【单选题】蒸馏不能分离以下哪种混合物：（ ）
A.
高沸点甲苯（b.p. 110.4 ℃ 和低沸点乙醚（b.p. 34.5 ℃)的混合液
B.
溶解有固体化合物的乙醇溶液
C.
乙醇（95%）与5%水的混合液