Помогите пожалуйста с заданием 2.2

The brain,which sends and receives messages twenty-four hours a day,never sleeps.
Hundreds of years ago scientists,who wanted to find out if everyones brain is the same size, studied the human brain.
They discovered that an adult brain,which weighs about 1,400 grams,is about 2% of our body weight.
The brain has about 10 billion nerve cells,which are called "neurons', that carry the messages around the brain.
Neurons,which start dying the moment we are born,do not grown again.