— My parents have been to Hongkong. 

— Really? When ______ there? [ ]

A. have they gone

B. have they been

C. did they go

D. will they go

下述哪项是乳腺癌出现表面皮肤凹陷的机制（）。

A.癌肿侵入乳腺管使其收缩

B.癌细胞堵塞 * * 皮下淋巴管

C.癌细胞浸润大片皮肤

D.癌肿侵犯Cooper韧带使其收缩

E.以上都不是