He talked about a hero ____ no one had ever heard.
A. of whom
B. from whom
C. about that
D. who
Combine the following sentences into an attributive clause.(将下列句子合并成一个定语从句。)1. The woman is our geography teacher. You saw her in the park.__________________________________________________________2. The magazine is mine. He has taken it away.__________________________________________________________3. The play was wonderful. We saw it last night.__________________________________________________________4. The fan is on the desk. You want it.__________________________________________________________5. The man is in the next room. He brought our textbooks here yesterday.___________________________________________________________________
携带有一个自主状态的F因子的菌株用
A. F+表示
B. F-表示
C. Hfr表示
D. F′表示。
既能以较高频率转移性因子,又能以较高频率转移细菌染色体片断的细菌是
A. F+菌株
B. F-菌株
C. Hfr菌株
D. F’菌株