crust

烤好的面包外皮呈金黄色。

The baked bread has a golden-brown ___crust.

地球的外壳主要由岩石构成。

The Earth's ___crust is mainly composed of rocks.

雪地上形成了一层坚硬的冰壳。

A hard ___crust formed on the surface of the snow overnight.