题目内容：

    Microplastics are everywhere in our environment. It's hardly surprising that the tiny fragments have also been found in humans. A new study shows that Americans are consuming as many as 121,000 particles each year.

Measuring 50 to 500 microns in length, microplastics come from a variety of sources, including large plastics that break down into smaller and smaller pieces. Therefore, much remains unknown about the common existence of these materials within the human body, as well as their impact on human health.

Hoping to fill in some of these gaps, a research team led by Kieran Cox, a PhD candidate at the University of Victoria, looked at 26 papers assessing the amount of microplastics in commonly consumed food items, among which are seafood, sugars, salts, honey, alcohol and water. The team also evaluated the potential consumption of microplastics through inhalation （吸入）using previously reported data on microplastic concentrations in the air and the Environmental Protection Agency's reported respiration rates. Based on these data, the researchers calculated that our annual consumption of microplastics via food and drink ranges from 39,000 to 52,000 particles. When microplastics taken in through inhalation are taken into account, the range jumps to between 74,000 and 121,000 particles per year.

The authors of the study found that people who drink exclusively from plastic water bottles absorb an additional 90,000 microplastics each year, compared to 4,000 among those who only consume tap water. "This shows that small decisions, over the course of a year, really matter and have an impact." Cox says. The new study, according to its authors, was the first to investigate "the accumulative human exposure" to microplastics. But in all likelihood, the research tells only a small part of the entire story. Collectively, the food and drink that the researchers analyzed represent 15 percent of Americans' caloric intake. The team could not account for food groups like fruits, vegetables and grains because there simply is not enough data on their microplastic content.

For those worried about microplastic consumption, cutting down bottled water is a good place to start. But to the heart of the problem, we have to stop producing and using so much plastic.

1.What makes it difficult to know microplastics commonly exist in the human body?

A.The quality. B.The quantity.

C.The shape. D.The size.

2.How did Kieran Cox's team calculate the potential consumption of microplastics?

A.By studying papers. B.By comparing the impacts.

C.By analyzing the data. D.By conducting experiments.

3.Which of the following is true according to the text?

A.Drinking less plastic bottled water helps to take in fewer microplastics.

B.The study is among the earliest to investigate human exposure to microplastics.

C.Cox's team gained comprehensive information of microplastics taken in by humans.

D.People consume 74,000 to 121,000 particles of microplastics per year from food and drink.

4.What is the best title for the text?

A.The Potential Problems of Microplastics

B.Microplastics Coming From Various Sources

C.Microplastics Found Within Human Bodies

D.The Impact of Microplastics on Human Health