What is the hardest natural substance on Earth?

Why are slow-twitch muscles more beneficial than fast-twitch muscles for cardiorespiratory fitness?

In some states, medical marijuana is legal. this means that people who need to take marijuana because of a medical condition may take it only with approval from the doctor. however, officers still advise these people not to drive while under the influence.what is the main reason for this? they would become dangerous to themselves and other people.they would not able to read and follow street signs.they would not be capable of staying in only one lane.they would become dangerous to wildlife that may be present.

What is the name of the device that senses the current flowing,tripping the circut,and cutting off the electricity