-- You're dropped __________ “s” in the word “across”.-- Oh, you are right, __________ letter “s” should be doubled like this “cross”.
A：a, a
B：an, a
C：an, the
D：the, a
若lim△x→0fx0+2△x-fx03△x=1，则f′（x0）等于（ ）
大金塔、下龙湾是下列哪组国家的著名景点（ ）
A. I want to buy some toys.
B. Go straight down this street. Turn left at the traffic lights.
C. Sure.
D. He is flying a kite.
E. They played basketball.
若∠α补角加上30°是∠α余角的3倍，则∠α=____ ．
