老师向学生们保证考试不会太难。

The teacher ___assured the students that the test wouldn't be too difficult.

提前付款能确保你得到想要的商品。

Paying in advance ___assures you get the desired product.

酒店经理向我们保证会提供免费的机场接送服务。

The hotel manager ___assured us of complimentary airport shuttle service.