题目

Thousands of years ago, Shennong, who had an ox (公牛 ) head and a human body, lived in the south of China. Seeing that local people were suffering from disease, he built ladders ( 梯子 ) and houses on a high mountain to keep hundreds of medicine plants. 1 ． This legend (传说 ) has made Shennongjia in Hubei an inviting place for tourists. 2 ． You can see natural scenery from all four seasons at different altitudes (海拔 ). “When the bottom of the mountain is summer, the top is spring and while the foothill is autumn, the top is covered with ice,” local people say of the speci请用微粒的观点解释：（1）酒香不怕巷子深，说明    ；（2）10mL精和10mL水混合后体积小于20mL，说明    ；（3）氧气、一氧化碳均含有氧元素，但氧气可供人呼吸，而一氧化碳有毒，说明    ．