Anna is an exceptional young girl. anna does any job that needs to be done.
to vary the sentence structure, which one of the following sentences should you insert in the blank?
a. anna works hard every day of her life.
b. anna is a hardworking and versatile person.
c. have you noticed how hard she works?
d. anna is always working hard at home.

In order to vary the sentence structure, the sentence I would insert in the blank is C. Have you noticed how hard she works? The reason for this is because inserting an interrogative sentence that has a completely different structure and word order than the other two sentences works great in order to introduce some versatility into a paragraph consisting of a couple of sentences. Here, the only sentence that differs is C. which is why you should choose it. Starting three sentences in a row with the same word can be a bit dull and repetitive.