Looking on the internet deeply has found these results:
I am not certain on what I am supposed to do. is the most popular phrase on the web.
I am not certain of what I am supposed to do.11 results on the web |
I am not certain on what I am supposed to do.1288,000,000 results on the web More popular! |
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Some examples and use cases from the internet: |
Some examples and use cases from the internet: |
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