Complete the following text with suitable verbs in the box with their right forms. $\begin{array}{|l|l|l|l|l|} \hline \textbf{reduce} & \textbf{are} & \textbf{have} & \textbf{is} & \textbf{adopt} \\ \hline \end{array}$ Environmental issues (a) — becoming more pressing each day. Many countries (b) — implemented policies to (c) — carbon emissions. However, there (d) — still challenges that need to be addressed. It (e) — essential for individuals to (f) — sustainable practices.