根据短文内容， 判断句子的正（T）误（F）。
If you are near-sighted and need to wear glasses all the time, you have to go to astore or hospital to
have your lenses (镜片) changed from time to time. John Silver, a professor at Oxford University, may
be able to help you.
He has invented a pair of glasses that the wearers can change the lenses themselves. The glasses are
based on a simple principle: the fatter the lens is, the more powerful it is. Inside each lens is a clear bag
filled with fluid (液体). The wearers can change the amount of fluid with a syringe to change the power
of the lenses.
The invention may be a great help to near-sighted people in the' developing world. In the UK, there
is one optometrist (验光师) for every 4,soo people, but in Africa only one for every l,000,000.
So far, professor Silver has made30,000 pairs of glasses, and has given them away to 15 countries.
He plans to offer them to a billion people in the world's poorest areas by 2020.
( )1. John Silver is an optometrist.
( )2. The word "principle" means "原理".
( )3. To make the new glasses more powerful, less fluid should be put into the bags in the lenses.
( )4. This kind of glasses will be useful in Africa because it's hard to find an optometrist there.
( )5. The passage mainly tell us about a famous inventor.