题目内容：

    When Omar Yaghi was growing up in Jordan, his neighborhood received water for only about 5 hours once every 2 weeks. If Yaghi wasn’t up at dawn to turn on the taps to store water, his family, their cow, and their garden had to go without. At a meeting last week, Yaghi, now a chemist at the University of California, reported that he and his colleagues have created a solar-powered device that could provide water for millions in water-stressed regions. At its heart is a porous crystalline  (多孔晶体) material, known as a metal-organic framework (MOF), which acts like a sponge: It sucks water vapor out of air, and then releases it as liquid water.

Yaghi and his colleagues first developed a zirconium( 锆 )-based MOF in 2014 that could harvest and release water. But at $160 per kilogram, zirconium is too expensive for massive use. So, last year, his team came up with an alternative called MOF-303, based on aluminum, which costs just $3 per kilogram, but the harvest was only about 0.2 liters per kilogram of MOF per day.

In July 2019, Yaghi reported that his team has designed a new and far more productive water harvester. Supported by a solar panel to power a fan and heater, which speed the cycles, the new device produces up to 1.3 liters of water per kilogram of MOF per day from desert air. Yaghi expects further improvements to increase that number to 8 to 10 liters per day. And his company plans to release a microwave-size device able to provide up to 8 liters per day this fall. The company promises an enlarged version next year that will produce 22,500 liters per day, enough to supply a small village.

However, it needs to be shown that Yaghi’s MOFs can be produced cheaply on a large scale. Each potential commercial MOF needs to prove itself in stability, efficiency, and life span. But if MOFs can pass those tests, they could offer a solution to some of the world’s most pressing problems.

1.Why is Omar Yaghi’s childhood mentioned at the beginning?

A.To show how serious water problem is. B.To lead in the topic.

C.To introduce the chemist. D.To arouse reader’s interest.

2.What is the problem of MOF-303?

A.It costs too much. B.It can’t last long.

C.It is hard to operate. D.It is low in efficiency.

3.According to Yaghi, how much water will a large water harvester produce per day?

A.1.3 liters. B.10 liters.

C.22,500 liters. D.8 liters.

4.What can be concluded from the last paragraph?

A.Yaghi’s MOFs are in great demand now.

B.Yaghi’s MOFs may help solve water shortage.

C.Yaghi’s MOFs have already entered the market.

D.Mass production of Yaghi’s MOFs is impossible.