1. An airplane flew from San Francisco to Washington, D. C.
Approximately halfway through the flight, the plane had traveled 2,000
km in 2.5 hours. What was the speed during this period?

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.