题目内容：

    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.

Studies have found higher rates of high blood pressure among people with the lowest sun exposure. 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. It reduces both heart attack and stroke risks. Vitamin D, which sunlight helps your body produce, is also linked to better health. So walk outdoors for 15 to 30 minutes daily.

In Japan, walking through forests to keep healthy has become a 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.

1.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

2.Sunbathing is 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

3.It’s believed that walking through forests can ________.

A.make people popular B.help breathe in fresh air

C.reduce blood pressure D.help escape noisy cities

4.The best title of the passage should be ________.

A.Nitric Oxide Has Magic Functions

B.Walking Barefoot Builds the Body

C.Sunbathing is Good for Health

D.Outdoor Activities Benefit the Heart