2011届高考英语素能提高题：Unit 2《Growing pains》（译林牛津版必修1）
Hair is one of the commonest parts of the body and something that is given a lot of attention.You’ve had it since birth and you take care of it every day.But how much do you know about your hair?
The average head of hair is made up of 120,000 strands(根)，each of which has a life expectancy of about three years.While some hairs are growing，others are resting，and others are falling out.
A hair is made up of two parts：the shaft(发丝)and the root.The shaft is a visible (or：seen) part.It has a complex structure.The root is the living part of the hair.It is here where cells develop and form the shaft.It also has a very complex structure.
