Explain how replacing asphalt with gravel or other permeable material can improve water quality.

As compared to gravel, asphalt is an impervious material, thus it allows water to flow over its top without infiltration. In this process the impurities present in the water do not get removed but is gathered and carried away till the maximum concentration point is reached and then removed at later stages. While if there would have been a permeable material like gravel etc, the impurities in water is not discarded but is retained due to infiltration at unwanted locations.  

cancer   is   essentially   uncontrolled   mitosis   of specialized cells