The correct answer is A. He and I both enjoyed the brownies you made.
Step-by-step explanation:
Capitalizing implies writing the first letter of a word in uppercase and the rest of the letters in a word in lower case, according to grammar the first word in a sentence should be always capitalized; additionally to this, proper names of places and people should be capitalized as well as names of months, days and holidays and also the pronoun I should be always capitalized. Considering this, "He and I both enjoyed the brownies you made" is capitalized correctly because the first word in a sentence "He" is capitalized and the pronoun "I", also any other words are not unnecessarily capitalized and thus the capitalization in this word is grammatically correct.