这张照片展示了各种各样的面部表情。

This photo shows a variety of ___expressions.

“冰山一角”这个表达常用来形容问题的表面现象。

The ___expression 'tip of the iceberg' is often used to describe the surface of a problem.

写日记是她表达情感的一种方式。

Keeping a diary is her way of ___expressing.

这个数学表达式可以简化为更简单的形式。

This mathematical ___expression can be simplified into a simpler form.