Identify the level of use of the following sentence. she's never looked so cool. formal general informal substandard

The correct answer should be informal.
Informal level of language involves the use of slang words, and cool is a slang word, so this sentence cannot be formal by any means. It is also not general due to a slang word being used. Substandard language would mean that it is not grammatically correct, and this sentence is, so this is also incorrect.