George is wasting his time and energy on pursuing a girl

I'd leave it out completely. He's wasting his time and energy doing this.

Grammar GeekI'd leave it out completely. He's wasting his time and energy doing this.

Thanks, GG.

If I have to choose one from the two prepositions, which one would you suggest?

If I had to use one, I'd use "on." I don't know that there's a lot of difference though.

Grammar GeekIf I had to use one, I'd use "on." I don't know that there's a lot of difference though.

Thanks, GG.

You use "on" because there is "wasting" in the front of the sentence, right? If it's "spending" in the front, would you use "in" or "on," to make sure?

I'd use "on" for "spending time" too.

Grammar GeekI'd use "on" for "spending time" too.

Thanks, GG.

But that doesn't correspond to what I've learned. The following are what I've learned:

George spent three hours in (not on)studying English yesterday.

George spent 1,000 dollors on (not in) this coat.

Correct me if I am wrong.

Let's go back to my original: I would use no preposition.

He spent three hours studying English. He's wasting time chasing that girls. I love spending time visiting museums.

I can only tell you that "George spent three hours in studying English" is not idiomatic American English. It may be BrE usage.

(I agree you spend money on things.)

Grammar GeekLet's go back to my original: I would use no preposition.

He spent three hours studying English. He's wasting time chasing that girls. I love spending time visiting museums.

I can only tell you that "George spent three hours in studying English" is not idiomatic American English. It may be BrE usage.

(I agree you spend money