以下哪项不是中厚皮片的优点（）

A.较柔软

B.能耐受摩擦

C.色素沉着轻

D.可生长在轻微感染经过适当处理的肉芽创面上

E.挛缩较少

______ quite recently, most mothers in Britain did not take paid work outside the home.

A．Before

B．Until

C．From

D．Since