watch out and u drop it
2.the only thing that it did was confusing me/....was confuse me??
3.how safer is it?/how much safer is it?
4.how much smarter is him

I'd also say that smart and smarter are US dialect; in the UK we wouldnt use that word, we'd say more intelligent or brighter
1. Watch out and you drop it.
2. The only thing that it did was confuse me.
3.How much safer is it?
4.How much smarter is he?

you're welcome.

A Texan
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in the second one shouldn't it be "was confusing me" there is a verb before confuse
A quick comment..

Shouldn't you have to put comma before (and) in No.1 because you are connecting two indepentent sentences.

No. 3 and No. 4
how save is it? How smart is he? is more appropritate for standalone questions.
safer/ smater (comparison) you have to show two subjects in the sentences..Right???

How much safer is it than something else?
How much smarter is he than someone else?

I am not sure about No.3 and No.4....If someone who know for sure..pls help.
 suzi's reply was promoted to an answer.
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and what about "what i did was confusing me"why i have to put confuse,if i have a verb preceding another verb