which sentence is correct: the students passed the exam last week or the students were passed the exam last week.

The students passed the exam last week.

Explanation:

Because the second sentence says the students WERE passed the exam last week and were doesn't need to be in there. Therefore it is not correct.

The students passed the exam last week. (first one)

Explanation:

The second one doesn't make much sense because were is present tense while passed is past tense.

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).