Why do scientific experiments need to be repeated? A. Because scientists often make mistakes

B. To ensure that the same results are achieved every time

C. They only need to be repeated if the results are questionable

D. To discourage other scientists from trying to get the same results

B. To ensure that the same results are achieved every time

Explanation:

Scientific experiments must be repeated multiple times because scientists can make mistakes in their experiments, and so they need to ensure they get the same exact result each time they do it. Scientists may make a mistake that they do not see, so they have to B. To ensure that the same results are achieved every time.

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.