根据短文内容，从短文后的七个选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Trampolining
What’s more fun than standing still? Jumping up and down on a springy piece of fabric (织物)! This activity is known as trampolining and it’s sweeping the nation．
The idea of trampolining is ancient．Eskimos have been throwing each other in the air for thousands of years．Firemen began using a life net to catch people jumping from buildings in 1887.
A gymnast named George Nissan and his coach Larry Griswold made the first modern trampoline in 1936.They got the idea by watching swing artists bouncing off of a tight net at the circus．They named their equipment after the Spanish word trampolín, which means diving board.
 In 1942 they began making trampolines to sell to the public.
Experts find that more than 100,000 people hurt themselves while using one each year．Clubs and gyms use large safety nets or other equipment to make it safer．Most trampoline injuries happen at home．Since trampolines are more affordable than ever, injuries are even more common.
These injuries happen for many reasons．People may bounce too high and land off of the trampoline or onto the springs．Perhaps the worst injuries happen when untrained people try to do flips (快速翻转)．Landing on your neck or head can cause injuries or even kill you.
But don’t let all that bad news keep you down．There are many things that you can do to practice safe trampolining．Trampolines have been around for a while now．They have brought a lot of joy to many people．They can be a good source of exercise and activity．But they can also be deadly．It is important to follow some professional guidance．Be sure that you are practicing safety while having a good time．Happy bouncing!

A．They can help people improve their balance and moves.

B．Trampolines may be fun, but they can also be dangerous.

C．The men wanted to share their idea with the whole world.

D．Injuries also happen when many people are jumping at the same time.

E． You can surround your trampoline with a net so that people don’t fall off of it．
F． They found a winner when they performed a piece of spring across a steel frame.
G． And in the early 1900s, circus performers began bouncing off of netting to amuse audiences．