thick-skinned

这种水果的厚皮保护它免受虫害。

The ___thick-skinned fruit is protected from pests.

即使被当面拒绝，他还是厚着脸皮继续推销产品。

Even after being rejected, he remained ___thick-skinned and kept pushing his products.

作为老师，你必须脸皮厚一些，才能应对学生有时无心的冒犯。

As a teacher, you need to be ___thick-skinned to handle students' occasional unintentional offenses.