By watching them in action通过观察他们的活动

in action在活动； 在运行中

He is a man gentle in manner but firm in action.

他是一个举止文雅但行动坚决的人。

Everything they eat comes from hunting and gathering.他们的食物都来自捕猎和采集

come from来自； 起源于

We heard clink come from that room.

我们听到那个屋子传来叮当声。

These creatures were believed to have come from outer space.

据信这种生物来自外太空。

as they set out to catch an evening meal for their families.为准备全家的晚餐出发前相见

set out to打算, 着手

They succeeded in what they set out to do.

他们打算做的事已经做成了。

The shepherd set out to look for the sheep that had wandered (away).

牧羊人出发去找走失的羊。