Question

7. The introduction of contaminants into a natural environment that causes changes in ma
ways is called
a) Climate change
b) Toxic substances
c) Pollution
d) Volcano eruption​

Answer 1

Explanation:

In insulators the valence band is fully occupied with electrons due to the covalent bonds. The electrons can not move because they're "locked up" between the atoms. ... This prevents the band gap, which lies in-between the valence band and conduction band.

Answer 2

Answer:

Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of chemical substances or energy, such as noise, heat, or light. ... Pollution is often classed as point source or nonpoint source pollution.

Explanation:

b) Toxic substances