Normal Boiling Points of Branched Alkane Hydrocarbons Generally Are Lower

Normal boiling points of branched alkane hydrocarbons generally are lower than for straight-chain hydrocarbons of the same molar mass because the straight-chain hydrocarbons ________

A) have stronger dipole-dipole interactions.
B) have many more electrons.
C) have more C-H bonds.
D) have a larger surface area and come in closer contact with each other.
E) react with each other to form long chains.