ensure doing sth.                              确保做某事
ensure that...                                确保……
ensure sth.to sb.                             保证给予某人某物
ensure (sb.) against/from sth.
                                              保护(某人)免受危害,
                                               使(某人)安全
①To ensure the child’s quick recovery, the doctor gave him an injection. 为了确保孩子尽快康复, 大夫给他打了针。 
②There must be safety devices to ensure workers against accidents.
一定要有保护工人避免工伤事故的安全装置。 
③Please ensure__that all lights are turned off.
请务必将所有的灯都关掉。