巴西是咖啡和可可等热带作物的主要供应国,在期货条件不变的情况下,如果巴西出现灾害性天气,则国际市场上咖啡和可可的价格将会()。
A.不变
B.不一定
C.下跌
D.上涨
参考答案:D
若⊙O1:x2+y2=5与⊙O2:(x-m)2+y2=20(m∈R)相交于A、B两点,且两圆在点A处的切线互相垂直,则线段AB的长度是( )。
Speaker A: I'd like to check in, please.Speaker B: ______
A.Certainly. Do you have a reservation
B.Sorry, I don't see what you mean.
C.Sure, I can help you with the checking.
D.Thank you, we provide first class service here.