Since (As) so many classmates are going to a lecture, we had better postpone (put off) the class meeting.
考点：had better：最好，用于表示对别人的劝告、建议或表示一种愿望，后面必须跟动词原形。postpone（put off）延缓，延迟。
句子结构：本题考查since或as引导原因状语从句。
