______ time went by , Herbert could finish all the maths  exercises in class.

A．With

B．As

C．while

D．Since

下列易恶变的体表肿瘤是

A．皮样囊肿

B．皮内黑痣

C．皮脂腺囊肿

D．多发脂肪瘤

E．交界痣