What is the definition of period?

The full stop (Commonwealth English), period (North American English) or full point . is a punctuation mark. It is used for several purposes, most often to mark the end of a declarative sentence (as opposed to a question or exclamation); this sentence-terminal use, alone, defines the strictest sense of full stop.

Explanation:

Is that the one ur looking for

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.