一种RnaseP酶是由20%蛋白质和80%RNA组成，如果将这种酶中的蛋白质除去，并提高Mg²⁺的浓度，发现留下来的RNA仍然具有这种酶相同的活性，这一结果表明(　　)

近几年来，台商投资的热点已经向以下哪个地区转移（ ）

新西兰是著名的乳畜业国家，其乳畜产品销往世界各地。左图为新西兰某地牧草成长与乳牛草料需求关系图，右图为该地气候资料。读图回答下列各题。

昼夜交替的周期是

完成对话
A: How was your vacation, Fred?
B: ____ .
A: ____ ?
B: I went to the U.S. with my parents.
A: Cool! ____  in the U.S.?
B: First we went to Los Angeles(洛杉矶). My uncle lives there. Then we went to New York to see my cousin.
A: ____ ?
B: It was a little warm but sunny.
A: Did you see any movie stars in Los Angeles?
B: No, but I saw Tom Cruise in New York. He was at a restaurant! I got his autograph.
A: Wow! That’s great!  What else did you do in New York?
B: Hmm…Oh yeah, I also went to Central Park.____ there! .