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

圈型卡环的适应证

A．下颌尖牙

B．前后均有缺隙的孤立后牙

C．上颌双尖牙

D．单侧游离缺失，修复体双侧设计

E．孤立并向近中颊舌侧倾斜的最后磨牙