The upper mesenteric plexus (UMP) also known as superior mesenteric plexus innervates the cecum. It also innervates the small intestine and parts of the large intestine (from cecum to the first 1/2 of the transverse colon).
Is from the upper mesenteric plexus-2. the cecum receives parasympathetic innervation from the vagus nerve-b and c are wrong. the upper mesenteric plexus does receive parasympathetic nerve fibers from the celiac plexus, but the parasympathetic fibers do not synapse there- remember parasympathetics tend to synapse in the walls of the target organ. so they are just passing through the celiac on the way to the upper mesenteric (and from there will synapse in the cecum).
regarding option c, its kind of a trick question. the thoracic splanchnic nerves form the celiac plexus, which gives off fibers to the upper mesenteric. think about the order of formation- the thoracic splanchnics come before the upper mesenteric, so they couldnt join the upper mesenteric (because without those nerves the upper mesenteric plexus doesnt exist). by the way, the superior mesenteric plexus does receive a branch from the vagus nerve.