Listen to a report about concrete that can repair itself. – Luyện nghe VSTEP Part 3 – Bài nói, bài giảng

1. What is the main problem with ordinary concrete?

A. It cracks and lets water in.B. It is too expensive.C. It is too heavy.D. It takes too long to make.

2. What is mixed into the new concrete?

A. bacteria and their foodB. steel and sandC. plasticD. limestone

3. When do the bacteria become active?

A. when the concrete is madeB. when water gets into a crackC. when it is very hotD. every few years

4. What do the bacteria produce?

A. waterB. steelC. sandD. limestone

5. Why is the new concrete not used everywhere yet?

A. It doesn't work in tunnels.B. It is not strong enough.C. It is much more expensive.D. It needs a lot of energy to make.