1. I want to learn what to drive.

2. I want to learn which to drive.
3. I want to learn whom to drive.
4. I want to learn that to drive.
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Which ones are grammatical? #4 is wrong,right?

4 Is not grammatically correct it would be I want to learn how to drive.

(Jamie needs to learn how to NOT write run-on sentences!)

I'm not sure what you're trying to say with these sentences.

3 and 4 are definitely not correct, but I'd need to know the context to be able to tell about 1 and 2.

Among the given options, the only grammatically correct sentence is:

1. I want to learn what to drive.

Explanation:
In this sentence, the word "what" is used correctly as a pronoun to ask about the object of the verb "drive." It indicates that the speaker wants to know which vehicle they should learn to drive.

For the other options:
2. "I want to learn which to drive." - This sentence is grammatically incorrect because "which" is used to ask about choices or options among known alternatives. However, in this context, it doesn't make sense to ask which vehicle to drive without providing any options.

3. "I want to learn whom to drive." - This sentence is grammatically incorrect. In English, we use the pronoun "whom" to refer to the object of a verb or preposition when it is the object of the verb "drive." Since we are talking about driving a vehicle, not a person, it is not appropriate to use "whom" in this context.

4. "I want to learn that to drive." - This sentence is also grammatically incorrect. It lacks clarity and doesn't form a proper question or request. It is missing a subject and therefore cannot be used to ask about or learn anything specific.

Therefore, the correct sentence is option 1: "I want to learn what to drive."