题目内容：

    It's already challenging enough for environmentalists to keep beaches clear of washed up trash(垃圾) and plastic debris(残骸), but the most difficult problem lies in cleaning up all of the millions of tiny microplastics that are impossible to pick up and separate from the sand.

Fortunately, a group of engineering students succeeded in developing a massive new vacuum cleaner that can collect microplastics without removing any of the sand from the beach. The 12 Canadian students from the University of Sherbrooke in Quebec built their Hoola One plastic vacuum cleaner as a class project.

"We did some research and we realized there was no machine around the world to do this kind of job," Hoola One co-founder Sam Duval told Hawaii Public Radio. "So we told each other, 'We will invent it,' and we did it."

As a means of testing their machine's efficiency, they recently used it on the sands of Hawaii's Kamilo Beach, which is also notorious for being one of the dirtiest beaches in the world. Though their first prototype(原型)experienced a number of technical issues, the students managed to fix the problems and tidy up the beach.

Using a handheld tube, the machine sucks(吸入)up plastic and sand and dumps them all into a massive tank of water. Since rocks and sand are heavier than plastic, they sink to the bottom of the tank so they can be dumped back onto the beach. The plastic, on the other hand, floats to the top of the tank.

According to Hawaii Public Radio, the team left the Hoola One vacuum on the island as a donation to the state department- They are now researching the ecological effects of the vacuum on the beach while they search for funding and sponsorships(赞助)to produce more Hoola One vacuums.

1.What is the hardest problem of keeping the beach clean?

A.Picking up plastic debris.

B.Removing trash on the sea.

C.Separating plastics from the sand.

D.Clearing up all the microplastics.

2.What do we know about the Hoola One plastic vacuum cleaner?

A.It can collect plastics without removing sand from the beach.

B.It has been used widely on the beaches around the world.

C.The students tested its efficiency on Hawaii's Kamilo Beach.

D.The students gave up the first prototype due to several failures.

3.What is Paragraph 5 mainly about?

A.The working procedure of the vacuum cleaner.

B.The invention process of the vacuum cleaner.

C.The ecological impacts of the vacuum cleaner.

D.The special materials of the vacuum cleaner.

4.What words can best describe the 12 Canadian students?

A.Generous and stubborn. B.Confident and persistent.

C.Devoted and wealthy. D.Admirable and humorous.