大肠杆菌的RNA聚合酶由数个亚基组成,下列哪一组是其核心酶()
A.α2β
B.α2βζ
C.α2ββ’
D.αβ
E.α2β’
参考答案:C
阅读下面的短文,判断正(√)误(×)。
Boy: How do we go to the park?
Girl: Let's go there by bike! Go straight from here. Then turn right. It's next to the hospital. Come on! Let's go.
Boy: No! Wait a minute. It's a red light.
Girl: Here it is, the north gate of the park.
Boy: The north gate? I want to go to the bookstore at the south gate. There is a fruit stand near it.
Girl: It's not far from here.
( ) 1. They go to the park by subway.
( ) 2. The park is next to the cinema.
( ) 3. They get to the north gate.
( ) 4. The fruit stand is at the north gate.
( ) 5. The south gate is far from the north gate.
已知等腰三角形的周长为10,其中一条腰长为x,则x的取值范围为( )。