Final answer:
The correct answer is d. isn't used to being.
Step-by-step explanation:
The correct answer is d. isn't used to being.
In the given sentence, the phrase 'yet' suggests that the puppy is still becoming accustomed to being around a lot of people. This indicates that the puppy is not yet used to being around many people. Therefore, the correct construction of the sentence would be 'isn't used to being.'
For example: 'My new puppy isn't used to being around a lot of people yet, so he gets nervous and hides under the couch when visitors come over.'
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