患者，女性，50岁，牙周治疗后右上后牙咬合疼痛1天，自感该牙有松动、伸长。检查：见右下7颊侧牙龈充血水肿，呈椭圆形肿胀突起，叩痛（++），松动Ⅰ度，牙周探诊6mm，X线片示根分叉区暗影。

导致该症状出现的因素是（）

A.机体抵抗力下降

B.牙周复杂袋沿牙根迂回曲折

C.深牙周袋的刮治术不彻底

D.刮治时动作粗暴，损伤牙龈组织

E.以上各项都可能

The nurse is caring for a primigravida who is scheduled for a fetal acoustic stimulation test (FAST). The nurse should explain to the client that the primary purpose of this test is to

A．induce contractions.

B．induce fetal heart rate accelerations.

C．shorten the contraction stress test.

D．determine fluid volume.