What is the difference between を vs の in 何を勉強します and 何の勉強します ?

I noticed in sentences both variants. And I wonder which of them more properly
or in which case they are should be used?

P.S.Neither english nor japanese are native languages ​​for me.
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2019-09-07T15:15:21.613
70624
2019-09-07T15:15:21.613
35292
question
particles particle-の particle-を
What is the difference between を　vs　の in 何を勉強します　and　何の勉強します?