Complete the following text with suitable verbs in the box with their right form. $\begin{array}{|l|l|l|l|l|} \hline \textbf{revise} & \textbf{help} & \textbf{understand} & \textbf{concentrate} & \textbf{forget} \\ \hline \end{array}$ To do well in exams, students should (a) ___ regularly. Group study can (b) ___ them (c) ___ better. If they (d) ___ sincerely, they will not (e) ___ what they read.