The teacher told the students___to__ {close} their eyes为什么要加to

The teacher told the students (not to close) their eyes.
解释：
tell sb not to do sth 告诉人不要做没事

tell sb to do sth 和 sb be told to do sth
分别翻译为 “告诉某人做某事” “某人被告诉做某事”

tell sb to do sth 告诉某人做某事
tell sb not to do sth 告诉某人不要做某事