The sheets of peritoneal membrane that hold the digestive tract in place are called

Mesentries

Explanation:

Mesentries are a set of tissues that is responsible for attaching to the parts of the digestive system such as the stomach, small intestine, spleen, and other organs that posterior side of the abdomen and thus helps to hold it in place. It further helps to store fat and allows to supply blood vessels and lymphatics to the intestine. 

Cand d are correct because the rest are just showing your mistakes and you don’t want people who are reading a summary you wrote to see all the mistakes you made.

Crossing over creates new combinations of genes in the gametes that are not found in either parent contributing to genetic diversity