Explaining on Instagram: "Follow (us) @Explaining to learn something NEW everyday 🧠💫 CPR, or Cardiopulmonary Resuscitation, is an emergency procedure used when someone’s heart stops beating. To do CPR, place the heel of your hand on the center of the chest, put your other hand on top, and push hard and fast at a rate of about 100–120 compressions per minute. If trained, give two rescue breaths after every 30 compressions. CPR helps keep blood and oxygen flowing until professional help arrives,

Do与does用法区分，一般现在时英语助动词，下面这些句子怎么用