Read the sentence.
In this sentence, the word "you" is a(n)
"You really should be careful when handling that
glass," instructed the teacher.
reciprocal pronoun.
subjective pronoun.
objective pronoun
intensive pronoun.
Subjective pronouns act as the subject of a sentence, and are at the start of the sentence. In this case, that proves that the word you is a subjective pronoun!
