There are two properties of phospholipids that affect how tightly they pack together: the length of ...

There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds.
 
  The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)?
  (a) 24 carbons with 1 double bond
  (b) 15 carbons with 2 double bonds
  (c) 20 carbons with 2 double bonds
  (d) 16 carbons with no double bonds