有关理想质粒载体的特点,正确的是()
A.为线性单链DNA
B.含有多种限制酶的单一切点
C.含有同一限制酶的多个切点
D.其复制受宿主控制
E.不含耐药基因
参考答案:B
According to the newspaper, the police are still looking for the criminal, who is still at ______.
A. large B. bay C. dawn D. dusk
慢性HBV感染是指HBsAg阳性持续()个月以上?
A.1
B.2
C.3
D.6