题目内容：

    Your circle of friends may help you get a better reading on your overall health and wellness rather than just using wearable devices such as a Fitbit, according to researchers.

The study, published in the journal PLOS ONE, analyzed what the structure of social networks says about the state of health, happiness and stress.

"We were interested in the topololgy (拓扑学) of the social network — what does my position within my social network predict about my health and well-being said Nitesh V. Chawla, a professor at the University of Notre Dame in the US.

“What we found was the social network structure provides a significant improvement in predictability of wellness states of an individual over just using the data obtained from wearables, like the number of steps or heart rate,” Chawla said.

For the study, participants wore a Fitbit to capture health behavior data about walking, sleeping, heart rate and overall activity level. They also completed surveys and self-assessments of their stress, happiness and positivity.

Cbawla and his team then analyzed the data with a machine learning model, alongside the connections and characteristics of an individual's social network.

The study showed a strong correlation (相关性) between social network structures, heart rate, number of steps and level of activity.

Social network structure provided significant improvement in predicting one's health and well-being compared to just looking at health behavior data from the Fitbit alone.

For example, when social network structure is combined with the data from wearables, the machine learning model achieved a 65 percent improvement in predicting happiness.

The model also achieved a 54 percent improvement in predicting one's self-assessed health prediction, a 55 percent improvement in predicting positive attitude and a 38 percent improvement in predicting success.

This study asserts (断言) that without social network information, we only have an incomplete view of an individual's wellness state, and to be fully predictive or to be able to obtain interventions (干扰). It is critical to be aware of the social network, Chawla said.

1.What did the study find?

A.How people choose their friend circles.

B.What factors decide your friend circles.

C.How your circle of friends influences you

D.What your circle of friends says about your health.

2.How did the researchers draw their conclusions?

A.By comparing data. B.By giving examples.

C.By analyzing cause and effect D.By describing personal experiences.

3.What does the underlined word “critical” mean in the last paragraph?

A.Easy. B.Common.

C.Important. D.Challenging.

4.What do Chawla's words in the last paragraph tell us?

A.How fitness devices can connect your circle of friends

B.That a person's social network is part of his health picture.

C.The best ways to make friends and keep a healthy social circle

D.That wearable devices are not useful for understanding someone's health.