Help me please and thanks

1. air mass -> large body of air with uniform temperature and humidity

2. cyclone -> a severe storm

3. front -> where two different air masses meet

4. source region -> area over which an air mass forms

primary succession begins with a bare rock and ends with a forest secondary succession begins after a natural disaster where there is a temporary setback after a forest fire or local destruction, but the surrounding area can fill in

the answer is b.) hydrogen bonds between bases.