In this task, you are given a question and answer for that. The answer will fill in the blank or will complete the unfinished question. Your task is to provide an explanation based on the given question or fill-in-the-blank statement, and answer.

Question: A piece of glass has _____ friction than a piece of sandpaper. 
 Answer: less
Rougher surfaces have more friction between them than smoother surfaces.

Question: Reid is modelling the greenhouse effect in a simulation. If he increases greenhouse gas levels, the greenhouse gas effect will 
 Answer: increase
An increase in greenhouse gases leads to greater greenhouse effect.

Question: A country like the US burns more fossil fuels than a third world country. This means that a richer country causes _____ pollution than a third world country. 
 Answer: more

Because richer nations use more fossil fuels, they also cause more air pollution and global warming than poorer nations do.