5. To ski can be dangerous.
滑雪有危险。
还能这样说：
It is dangerous to go to ski.
There may be danger in skiing.
谚语：
A danger foreseen is half avoided.
预见隐患等于防范一半。
6. My favorite winter sport is skiing.
我最喜欢的冬季运动是滑雪。
还能这样说：
I like skiing best among the winter sports.
I am most fond of skiing among the sports.
谚语：
Pain past is pleasure.
无论多么困难一定要咬咬牙冲过去，将来回忆起来一定甜蜜无比。
7. Skiing is one of the major events of Winter Olympics.
滑雪是冬奥会的主要竞赛项目之一。
还能这样说：
Skiing is one of the important sports activities in Winter Olympics.
Skiing is among the most significant events in Winter Olympics.
谚语：
All things are difficult before they are easy.
凡事必先难后易。
8. He is passionately addicted to skating.
他酷爱溜冰。
还能这样说：
He has a great passion for skating.
He is fascinated with skating.
应用解析：
addict oneself to 沉溺于，醉心于；
be addicted to 嗜好，热衷于