Select all of the following that are correct about mechanical waves. They can be longitudinal.
They can propagate in a vacuum.
They can be transverse.
They can propagate in a physical medium.
They transfer energy from particle to particle.

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.