If the carbon dioxide levels (choose one: increase/decrease/stay the same), then the average global temperatures will (choose one: increase/decrease/stay the same)
over time.

1. increase

2. increase

If the carbon dioxide levels increase, global temperatures will increase, because carbon dioxide is a greenhouse gas.

If I chose stay the same, this is what would happen:

If the carbon dioxide levels stay the same, global temperatures will stay the same because not too much or less carbon dioxide is being emitted to the atmosphere.

If I chose decrease, this is what would happen:

If the carbon dioxide levels decrease, global temperatures will decrease because there will be less greenhouse gases to make the atmosphere warmer.

Hope this helped you!