2010年8月7日夜22点左右,甘肃甘南藏族自治州_______县发生特大泥石流。8月15日全国举行哀悼活动,停止一切公共娱乐。[ ]
A、玉树
B、汶川
C、舟曲
D、天水
答案:C
Passengers on board aren't allowed _____ calls during take-off.
A.making or receiving
B.to make or receive
C.to have made or received
D.having made or received
当k=( )时,多项式x2-(3k-1)xy-3y2+6xy-8中不含xy项。