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 is a hardworking and versatile person.
b. anna is always working hard at home.
c. have you noticed how hard she works?
d. anna works hard every day of her life.

The correct answer is C) have you noticed how hard she works? 

Anna is an exceptional young girl. Have you noticed how hard she works? Anna does any job that needs to be done.

That is the correct option to vary the sentence structure.

In grammar, there are four types of sentence structure. We have simple, complex, and compound-complex structure.

A simple sentence has one independent clause. Comñpund sentences have two or more independent clauses. Complex sentences have an independent clause and a dependent clause. Compound-complex sentences have at least two independent clauses and one or more dependent clauses.

whether dad arrives in time for the game depends on his conference. subject