问题补充：
Only when their children leave home .
A. many parents did feel a sense of loss
B. did many parents feel a sense of loss
C. did feel many parents a sense of loss
D. do many parents feel a sense of loss
答案：
A. many parents did feel a sense of loss
B. did many parents feel a sense of loss
C. did feel many parents a sense of loss
(答案→)D. do many parents feel a sense of loss
解析：句意：只有当孩子们离开家时，许多父母才感到有种失落感。考查Only+when从句放在句首时，用部分倒装。
