商品谷物农业与季风水田农业相比,生产所需的共同条件是[ ]
A.有广阔的市场
B.地形平坦、土壤肥沃
C.地广人稀
D.有便利的交通运输
答案:B
Two hundred multiples of seven are chosen at random, and 300 multiples of eight are chosen at random. Approximately what percentage of the 500 selected numbers are odd ?()
A. 20%
B. 25%
C. 40%
D. 5O%
E. 80%
下图示哺乳动物(或人体)激素分泌的调节过程,图中腺体代表甲状腺,①至⑤表示五个过程。据图回答:
人体长期缺碘将会导致甲状腺增生(俗称大脖子病),这是因为缺碘会造成()分泌不足,导致过程()填序号)加强所致。