Answer:
d. Add sentence variety.
Step-by-step explanation:
The paragraph lacks sentence variety because it consists of short sentences that have a similar or parallel structure. In order to improve this, the paragraph should include transitional phrases and conjunctions, as well as a wider range of sentence constructions such as making longer statements. For instance:
Venice was an interesting destination. One of the reasons is that you have to travel by boat. Apart from that, we toured a chandelier factory with incredible colored glass and enjoyed the artwork in the museums, which were crowded with tourists.