Some deer in Minnesota rely on a team of bats to eat up biting flies 【小题1】 typically trouble them. Researchers observed this 【小题2】 (previous) unknown symbiotic (共生的) relationship between white-tailed deer and an unidentified bat species at the Cedar Creek Ecosystem Science Reserve.

“These bats appear 【小题3】 (attract) by all the flies around the deer,” says study leader Meredith Palmer. Symbiotic relationships between mammals (哺乳动物) and birds are better known, she says, but “【小题4】 is very rare for mammals to help each other like this.’’

This bat-deer 【小题5】 (associate) is a positive interaction that benefits at least one, perhaps even both 【小题6】 (partner). Bats may save search time and energy by 【小题7】 (feed) on the flies, and this feeding could bring the deer much needed relief in the summer months. The study 【小题8】 (publish) in March in Ethology.

Craig Willis, a biology professor at the University of Winnipeg in Manitoba, says, “If the bats are reducing biting insects for deer, maybe they can also do the same for humans.”

Ecological research seldom 【小题9】 (focus) on the positive ways in which animals help one another, Palmer notes. 【小题10】 it comes to beneficial symbiotic relationships, she says, “there’s just a big gap out there.”

A British math expert says all the COVID-causing virus that 【小题1】(current) exists in the world could easily fit inside a single can of soda. The finding shows just how much damage can 【小题2】(cause) by very small virus particles.

Christian Yates of the University of Bath studied worldwide rates of new COVID-19 infections and made estimates of the amount of virus in 【小题3】 infected person’s blood. He found that there are about two quintillion - or two billion billion - SARS-CoV-2 virus particles in the world at any one time.

Yates said he came up 【小题4】 that result by measuring the distance across one virus particle - about 100 nanometers, or 100 billionths of a meter. He then found the total amount of space 【小题5】 the virus takes up.

He said the total is still less than can be contained in a single 330 milliliter soda can. He noted that total includes the fact that the particles will leave a lot of space in between when 【小题6】(place) together.

“It’s 【小题7】(astonish) to think that all the trouble, the disruption, the hardship and the 【小题8】(lose) of life that has resulted over the last year could constitute just a few mouthfuls,” Yates said in a report on his findings.

More than 2.3 million people 【小题9】(die) in the COVID-19 pandemic so far. There have been about 107 million confirmed 【小题10】(case) worldwide.

There are three 【小题1】 (type) of burns. They are called first, second or third degree burns, 【小题2】 (depend) on which layers of the skin are burned.

First degree burns affect only the top layer of the skin. These burns are not serious and should feel 【小题3】 (good) within a day or two. Examples include mild sunburns and burns caused by【小题4】 (touch) a hot pan, stove or iron for a moment.

Second degree burns affect 【小题5】 the top and the second layer of the skin. These burns are serious and take a few weeks 【小题6】 (heal). Examples include severe sunburn and burns 【小题7】 (cause) by hot liquids.

Third Degree burns affect all three layers of the skin, 【小题8】 any tissue or organs 【小题9】 the skin. Examples include burns caused by electric shocks, burning clothes or severe petrol fires. These burns cause very severe 【小题10】 (injure) and the victim must go to hospital at once.