1. This candle will keep the room

bright.

2. This candlelight will keep the room
bright.

Can both be used? Which one is frequently used?)

3. We breathe with our noses.
4. We breathe through our noses.
(Are both OK?)

5. We could not go on a picnic because of rain.

6. Rain prevented us from going on a picnic.

(Are both the same? And can we use 'thanks to' instead of 'because of'?))

7. He kept on running.
8. He kept running.

(What is the difference between them?)

2 answers

1 is better than 2; #2 has the word "light" repeated unnecessarily.

4 is better than 3.

5 and 6 are saying the same thing. Yes, you can use the expression "thanks to" instead of "because of" -- it's rather sardonic!
http://www.answers.com/sardonic

There is little difference between 7 and 8. They are saying the same thing.
With 1 and 2, "candle" indicates one candle, while "candlelight" can be coming from multiple candles.

I hope this helps a little more. Thanks for asking.