Most candidates who attempted this question could explain the terms population and competition but performed poorly in trying to explain Succession. 
The expected answers include:
Succession  -   This is the step by step/orderly; and gradual replacement of   communities; arising from a change in the environment/  environmental factors; which leads to a climax stable community.

The candidates equally performed well in stating the sources of noise pollution as well as the means by which they can be prevented but some candidates listed factories as sources of noise pollution instead of factory machineries and so lost the mark.

Most candidates also performed well on effects of smoke and sewage on humans.