My sister is tall.

The correct answer is: She

The correct answer is "she".
From the above-mentioned example, we can say that the speaker's sister is tall. Here, the subject is the speaker's sister and to represent it, we must use a third person singular number pronoun. Among the given options, the words "he" and "she" have a similar feature, but since Alice is a girl, a feminine gender pronoun must be used. So, the correct answer is "she".