单选题 Having finished their morning work, the clerks stood up behind their desks, ______ themselves.
【正确答案】 B
【答案解析】解析：句意：完成上午的工作后，职员们在桌后站起来，舒展他们的身体。B项stretching常用于表示舒展身体，故为答案。A“扩张”、C“延长”和D“延续”均不能用于修饰身体，故排除。