Read the text and answer the questions.

To start with, we cannot go on using oil for ever. We can do so for a few more decades
– perhaps until 2070, then it will run out. There will be none left – or at least, there will be hardly any left. At present, there is still plenty of oil under the ground. Engineers keep finding new sources of oil. But there are some realities which cannot be avoided.
The quantity of oil under the ground and under the sea is not infinite. It will not last for ever. As oil becomes rarer, it will become harder to extract. It will also become more and more expensive. It will therefore become more expensive than other fuels. Oil will always cause pollution.
However, scientists are making new forms of oil, using plants. Most of the oil that we eat comes from plants; and it is sometimes possible to make petrol from this oil. For instance, some types of diesel-fuel already contain sunflower oil.
Sunflowers produce oil too; but most of this oil is needed for cooking. Sunflower oil is cleaner than mineral oil, so it causes less pollution. But perhaps, in the long term, vegetable oils are not a good solution for the future; in the future we may need all the land for producing food. In reality, the future will have to be a future without oil – or with very little oil. Scientists are already developing cars, houses and plastics that do not use oil.
Electricity will be the energy of the third millennium, but it will have to be clean electricity. Today, electricity is produced in several different ways; some of it is produced using oil; but already oil-burning power-stations are being closed. Nuclear power-stations will be closed too, because they are very expensive and people do not want them.
Tomorrow's electricity will be made from gas, and from "renewable sources". In the long term, all our energy will come from "renewable sources" – including water! The sun, the wind, the rivers and the oceans will give us all the energy that we need! It will be clean energy
– with no pollution – and it will last for ever.
We are not there yet, however! The twenty-first century will be a century of change. People who are over 50 today are not going to see a world without oil. Those who are under twenty may perhaps do so. if they live long enough.

Complete this résumé of the article, putting appropriate words in the blanks.

Oil is one of the most important of in today's world; but unless we finding more and more, it will not for . In less than a century, it will . Most of the oil we comes from the ground, but some comes from .
But plants cannot produce all the oil we.
In tomorrow's world, we will use oil and more, but most of this will have to come from.
In thewe will use a lot of, but later we will have to get our from natural forces.