VOA慢速英语:美国学校考虑新的方法来对付枪手

tackle - v. to forcefully seize (someone) and cause that person to fall to the ground

alert - adj. able to think clearly and to notice things

lock - v. to fasten the door, lid, etc., of (something) with a lock

counter - v. to do something in defense or in response to something — often + with

evacuate - v. to remove (someone) from a dangerous place

confuse - v. to make (someone) uncertain or unable to understand something

grab - v. to quickly take and hold (someone or something) with your hand or arms

principal - n. the person in charge of a public school

barricade - v. to block (something) so that people or things cannot enter or leave

option - n. the opportunity or ability to choose something or to choose between two or more things