Final answer:
The most highly mobile phospholipid amongst the given options is c) 20 carbons, 2 double bonds, due to the introduced kinks from the double bonds which prevent tight packing and increase membrane fluidity.
Step-by-step explanation:
The student's question is asking which phospholipid would be the most highly mobile based on the number of carbons and double bonds present. Mobility of phospholipids is influenced by the length of their fatty acid tails and the presence of double bonds. Shorter chains and a greater number of double bonds in the fatty acid tails increase fluidity of the membrane because they prevent the fatty acid chains from packing tightly together.
The correct answer to the student's question is option c) 20 carbons, 2 double bonds. This phospholipid has a moderate length chain and two double bonds which introduce kinks into the fatty acid chains, preventing tight packing and thus enhancing fluidity. In contrast, phospholipids with longer chains and no double bonds would pack more tightly and be less mobile.