1. The answer is A: size. Magnitute means large size or great importance. Ripple effect means one event producing effects that produce further effects.
2. The answer is C: rubbish. Debris means broken or torn pieces of something larger.
3. The answer is C: spread. Dispersed means to scatter or move away over a large area, or to cause this to happen.
To combust: to start to burn.
To wade: to walk through water
To leak: to allow liquid or gas to escape.