Don't go hiking alone here. You _____ get lost. [ ]
A. can
B. must
C. may
D. should
答案:C
下列哪种食物最适宜原发性骨质疏松症患者补充锌()。
A.西瓜
B.牡蛎
C.南瓜
D.蘑菇
E.辣椒
芳烃抽余油也是很好的乙烯原料,裂解后乙烯收率与石脑油相近。