TASK DEFINITION: In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.
PROBLEM: Question: Carbon dioxide does not rise like other gases because it has a density greater than what? Answer: air

SOLUTION: Carbon dioxide does not rise like other gases because it has a density greater than air.

PROBLEM: Question: What type of friction is friction that acts on objects when they are sliding over a surface? Answer: sliding friction

SOLUTION: Sliding friction is friction that acts on objects when they are sliding over a surface.

PROBLEM: Question: In the past, what colliding with planet earth has caused many organisms to die off? Answer: asteroids

SOLUTION:
In the past, asteroids colliding with planet earth has caused many organisms to die off.