合成后无需进行转录后加工修饰就具有生物活性的RNA是( )。
A.tRNA
B.rRNA
C.真核细胞mRNA
D.原核细胞mRNA
参考答案:D
造成柴油机飞车的原因之一调速器(),拉杆卡住。
—Is that your pencil?
—______. That is her pencil. [ ]
A. Yes, it is
B. No, it is
C. No, it isn't
D. Yes, it isn't