他一眼就能看出有什么不对劲。

He could tell ___at ___a ___glance that something was wrong.

经验丰富的医生常常能一眼就诊断出病情。

An experienced doctor can often diagnose a condition ___at ___a ___glance.

看到他们的表情时，我立刻就明白了整个情况。

I understood the entire situation ___at ___a ___glance when I saw their expressions.