Which of the sentences shows the correct words to emphasize in a question/answer format?

a.
Do we need the greenhouse effect? You bet your thermal pj’s we do. Without it, Earth’s average temperature would be a nose-numbing 60 degrees Fahrenheit colder.
c.
Do we need the greenhouse effect? You bet your thermal pj’s we do. Without it, Earth’s average temperature would be a nose-numbing 60 degrees Fahrenheit colder.
b.
Do we need the greenhouse effect? You bet your thermal pj’s we do. Without it, Earth’s average temperature would be a nose-numbing 60 degrees Fahrenheit colder.
d.
none of these