skin是单数

例句

1、

New skin had to be grafted on from his back.

需从他的背部移植新皮肤。

2、

Even if you have dark skin， you still need protection from the sun.

即使你皮肤黝黑，仍需要防晒。

3、

The skin on her hands was hard and rough.

她手上的皮肤粗糙而没有弹性。