Complete the following text with suitable verbs in the box with their right form. $\begin{array}{|l|l|l|l|l|} \hline \textbf{cause} & \textbf{affect} & \textbf{stop} & \textbf{take} & \textbf{increase} \\ \hline \end{array}$ Pollution is a major problem that (a) — our environment. The number of vehicles and factories (b) — day by day. These (c) — serious air pollution which (d) — human health badly. We must (e) — steps to reduce it.