大肠杆菌是生物工程中常用的一种微生物。下列有关它的叙述正确的是  [ ]

A．可在含青霉素的培养基中生长

B．可以用含有高浓度的NaCl的培养基将其筛选出来

C．它属于原核生物，其同化作用类型为异养型

D．在同时含有葡萄糖和乳糖的培养基上，它只能分解葡萄糖，说明了它分解葡萄糖的酶是诱导酶

Up to now, the poet has written eight poems, three ___ are about American country life.

A．of them

B．in them

C．of whom

D．of which