题目内容：

    As they reach school age, about 90 percent of children will have experienced a condition in which fluid (液体) fills the middle ear, muffling (使模糊) sound and sometimes causing infection. The fluid usually clears on its own, but if not, it can lead to a painful ear infection called acute otitis (中耳炎) media. In some cases the fluid can persist for more than a year, causing hearing loss during this period, and slowing down their development of language and social skills.

Diagnosis usually requires a visit to a specialist—but researchers have now developed an app that detects this fluid just as accurately, with only a smartphone and a paper funnel (漏斗).

Doctors typically detect the problem by peering into the ear for a visual assessment. Yet, this method has only a 50 percent accuracy rate. “Right now, if you bring your child to a pediatrician, or to any urgent care family doctor, the way they look at whether or not there’s fluid in the middle ear is by looking at the eardrum,” says Sharat Raju, a surgeon in the department of head and neck surgery at the University of Washington.

For a cheaper and more accessible alternative, researchers at the University of Washington turned to smartphones. First the user follows a template to cut and tape a piece of paper into a funnel, which can be placed between a smartphone and the patient’s ear. Next the app plays a chirping sound through the phone’s speaker; the sound waves bounce off the eardrum and hit the phone’s microphone, where they register and are analyzed by the app. An eardrum with fluid behind it will vibrate (振动) differently than if the middle ear is full of air, as it normally is.

To develop the app, the researchers first played chirps for patients with and without fluid in their ears. They recorded the echoes (回音), which indicate the eardrum’s mobility. Then they used a machine learning model to classify the returning sound waves, determining which audio characteristics indicated a normal ear and which suggested the presence of fluid. Once they tested the app on 98 children, ranging from 18 months to 17 years old, at Seattle Children’s Hospital. It correctly detected fluid in 85 percent of cases, and correctly identified fluid-free ears in 82 percent.

The researchers are currently trying to get FDA approval for the app, and have founded a company to commercialize it. They hope to make it available by the end of the year, to help parents track children’s ear health at home.

1.What do we know about the fluid from the first paragraph?

A.It is mostly part of children’s growth. B.It is unavoidable for any child.

C.It is a permanent physical condition. D.It is beyond any medical means.

2.What does the underlined word “pediatrician” refer to in Paragraph 3?

A.A hospital. B.A specialist.

C.A relative. D.An app.

3.What is the fourth paragraph mainly about?

A.The application of the app. B.The causes of the kid’s ear problem.

C.The purpose of developing the app. D.The experiment of the smartphone.

4.What do the researchers expect of the app?

A.It will upgrade the medical technology. B.It will hit the market in the near future.

C.It will help children do better academically. D.It will save doctors medical operations.