一般认为 make sure 是固定搭配，不一定要分清这个 make 是什么动词。如果一定要区分的话，这个 make 可分析为连系动词，即 make sure 为系表结构。为了证实这一观点，我在张道真《英语语法大全》的第1472节查到了相关的依据：

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一些其他系动词也可用于这种结构：

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He stood mute with rage.

The burden sat light (or easy) on me.

The custom passes current among mountaineers.

The remarks passed unnoticed by all present.

She fought shy of him (or canned food).

He made merry over another’s mishap.

I must make sure of his address.

He makes free with my money.

They made ready for the fight.