The flight to Guangzhou had to be________because of the heavy snow.
A:put up
B:put out
C:put off
D:put down
函数y=log12x2-2x的单调递减区间是____
根据句子理解,用选词中的正确形式填空。
luck, feel stressed, make a decision, laugh at, correct
产生克隆羊多利的卵细胞的细胞核来自于( )
It's ____.
平均海拔在4000米以上,是世界最高的大高原,素有“世界屋脊”之称( )