阅读下面短文,在空白处填入1个适当的单词或括号内单词的正确形式。
Mountain climbing has appealed 21 many people. With more and more mountain climbing 22 (sight) developed, people are getting more chances to experience this exciting sport.
Those who aren’t brave enough to climb a mountain but still want to get a similar experience can go for man-made rock climbing wall. While mountain climbing is more difficult and dangerous and needs 23 (great) focus, the man-made rock climbing wall is less dangerous as the person just needs to climb a cliff(悬崖) 24 is not so high as a mountain.
Climbing man-made rock wall doesn’t need much skill and can 25 (do) with the help of a coach even if you don’t have any knowledge about the sport. However, those 26 (plan) to go for mountain climbing must have information about how this sport is carried out, though they needn’t learn the knowledge of mountain climbing 27 (thorough).
It is also important 28 (make) sure that you are fit to take part in this sport. 29 is suggested that you speak to someone with the first-hand experience of mountain climbing before planning to take up the sport.
I have tried climbing man-made rock wall with incredible 30 (brave) and the experience is very good. I would also like to try mountain climbing and I need to get enough courage for it first.