Final answer:
The soft connective tissue in the spleen is called reticular connective tissue, which is a mesh-like framework for soft organs. Reticular cells produce fibers that form a network and provide support. Therefore, the correct option is D.
Step-by-step explanation:
The soft connective tissue in the spleen is called reticular connective tissue. Reticular tissue is a mesh-like, supportive framework for soft organs such as the spleen, liver, and lymphatic tissue. Reticular cells produce reticular fibers that form a network onto which other cells attach.