A：省、自治区、直辖市
B：自治州、自治县、市
C：乡、民族、镇
D：省、县、乡
–There is little ________ at home. Let's go and buy some apples, pears and strawberries.–OK, we'll go to the supermarket in a minute.
用显微镜观察装片时，欲观察的结构在视野的左上角，应向____ 方移动装片，能使欲观察的结构移至视野中央．
