---______ the farmers discovered the entrance to the secret cave in the valley?

--- Totally by chance.

A．When was it that

B．How was it that

C．How it was that

D．When it was that

以下意见正确的是（）

A.后天性面部畸形和缺损，年龄越小手术效果越好

B.面部整复手术与生长发育无关

C.面部整复手术与年龄大小无关

D.面部整复手术最好在生长发育成熟后施行

E.整复手术对老年病员无必要进行