单项选择题

For years scientists have been worried about the ___________ of air pollution on the earth’s natural conditions.
 A.effect B.result C.account D.cause

<上一题 目录 下一题>
热门 试题

单项选择题
--- It’s been a wonderful Halloween Party. Thank you very much. --- .A.My pleasure B.I’m glad to hear that.C.No, thanks D.It’s OK
A.   
B.
C.
单项选择题
下列反应的离子方程式书写正确的是2O＝AlO2－＋4NH4＋＋2H2O－＋HCO3－＝CaCO3↓＋H2O3＋2H＋＝Ca2＋＋CO2↑＋H2O2＝2Fe3＋＋2Cl－
相关试题