相同材质的铁在图中的四种情况下最不易被腐蚀的是[ ]
A.
B.
C.
D.
答案：C
遗传因子组成为AaBb的个体，不可能产生的配子的基因型是[ ]
A．AB
B．ab
C．Bb
D．aB
At the end of last month, ten primary schools ______ with the help of Project Hope.
A．had set up
B．had been set up
C．set up
D．were set up
