The correct answer is D. None of the above.
The sentence “I am not as tall as …” is a comparative sentence. In a comparative sentence, we are comparing two things. In this case, we are comparing the speaker’s height to someone else’s height.
The subject of the sentence is “I.” The verb is “am.” The direct object is “tall.” The indirect object is “as.” The comparative adjective is “not as.”
The only option that is a comparative adjective is “not as.” The other options are pronouns. Pronouns are words that take the place of nouns. In this case, the pronouns “he,” “her,” and “she” could all take the place of the noun “someone.”
However, pronouns cannot be used in comparative sentences. In a comparative sentence, we need to use a comparative adjective. A comparative adjective is an adjective that compares two things. In this case, we are comparing the speaker’s height to someone else’s height.
The comparative adjective “not as” is the only option that can be used in this sentence. Therefore, the correct answer is D. None of the above.