But nobody saw a frog at all.

但是还是没有人看到有青蛙。

youdao

A mottled snake was sheltering from the heat among the roots of an old tree when he saw a frog coming.

一条花蛇正在一棵老树根下乘凉，看见对面来了一只青蛙。花蛇笑着说：“啊哈！”

youdao

One day, a tiger saw a frog. He had never seen a frog before. He said, "I want to eat you. But first tell me who you are."

一天老虎看见了一只青蛙，它以前从没见过青蛙，便说：我要吃了你，但你要先告诉我你是什么东西。

youdao

In the late 1800s English physiologist John Langley discovered the muscular nicotinic receptor when he tied a frog muscle to a round drum, put nicotine on the muscle and saw it contract.

FORBES: The Nicotine Cure