The potential energy in molecules is stored in...

Energy, potential energy, is stored in the covalent bonds holding atoms together in the form of molecules. This is often called chemical energy. Except at absolute zero (the coldest temperature it is possible to reach), all molecules move.

Chemical energy

Explanation:

Energy, potential energy, is stored in covalent bonds holding atoms together in the form of molecules

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.