如果是引述老师的话,选择过去时:Our teacher told us not to be nervous in the examination.或者是老师建议我们考试不必紧张,就是沉着的意思: Our teacher advised us to act calm in the examination.
Our teacher told us to be less serious in the exams.这里的紧张不是不好意思的那种紧张,所以用serious更好
希望能帮到你 呵呵
the teacher told us not to be nervers when we are in the test