Read the excerpt from Passage 2, Paragraph 4.
Bus engines are often left running while they wait for students at the end of the day; those buses churn out fumes that are harmful to both the environment and the students. Requiring thoughtless drivers to kill the engines reduces pollution and makes the air around the school more breathable for young students.
What is the meaning of the word kill as it is used in this paragraph?
to cause the death of
to put an end to
to cause to stop
to positively impress