Why is this sentence wrong She has good command in English?

The sentence "She has good command in English" is grammatically incorrect because it uses the preposition "in" incorrectly.

Here's why:

* "Command" in this context refers to mastery or control. We use "command *of*" something, not "command *in*" something.

Correct ways to say it:

* She has a good command of English.

* She has a good command in the English language.

* She is proficient in English.

* She speaks English well.

The correct preposition "of" indicates possession or control over the language.