Help please Why do scientists believe the universe is expanding?
The Doppler effect shows stars with red shifted light.
The Doppler effect shows stars with yellow shifted light.
The Doppler effect shows stars with green shifted light.
The Doppler effect shows stars with blue shifted light.

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.