popular practice. Apparently they want to enjoy the fresh air. But research on 280 volunteers found that people had a reduced heart rate, and lower blood pressure when they walked through a forest than when they spent time in an urban area.

　　One of the consequences of modern society is that rarely is our body in direct contact with the ground. The earth has an electrical current. Direct contact with it may be stabilizing force for good health. Although "earthing" or "grounding" is considered alternative by mainstream medicine, research shows that the practice seems to be able to reduce heart disease risks.

　　So, walk around barefoot wherever possible, let your backyard grass tickle your feet, and dig your toes into sandy beaches.

　　【语篇解读】　本文是一篇议论文。作者通过叙述自己的经历、感受和一些研究发现，告诉人们户外活动有益于心脏。

　　【难句分析】　One reason may be due to nitric oxide (一氧化氮), a gas whose function is activated when your skin is exposed to the sun's rays.

　　分析：本句包含whose引导的定语从句，修饰先行词a gas；when引导时间状语从句。

　　译文：原因之一可能是当你的皮肤暴露在阳光下时，一氧化氮的功能被激活。

　　5．The first paragraph is meant to ________.

　　A．show the author likes the song very much

　　B．put forward the argument of the passage

　　C．suggest that the author loves nature crazily

　　D．indicate the author is a Michigan native

　　答案与解析：B　考查推理判断。根据第一段"Whenever I hear a recording of John Denver singing'Sunshine on My Shoulders'， I find myself smiling, drawn to a love of the sun and the outdoors I've had for years as a Michigan native. Walking barefoot to the lake, playing without shirts in the sunlight, and breathing fresh air feel good. As a doctor I can tell you they are also good for your heart"的描述可知，作者写这段的目的是为了提出文章的论点。

　　6．Sunbathing's good for heart because ________.

　　A．the sun's rays make nitric oxide work

　　B．sunlight can help people keep warm

　　C．the sun's rays can help replace vitamin D

　　D．vitamin D reduces blood circulation

答案与解析：A　考查推理判断。根据第二段中的"One reason may be due to nitric oxide (一氧化氮), a gas whose function is activated