Amechanical wave is created when a medium or moves back and forth or up and down.

B hypha and D rhizoids

Explanation:

most of the fungi are saprotroph. They secretes digestive enzymes from hypha (B) of the mycelium on the dead and decaying matter. Digestive enzymes digest complex organic materials into simpler and soluble form in the external medium. With the help of root like structure called rhizoids (D) absorb nutrients from external medium into their body.