【Knuckle-popping（指关节砰砰响）Doyouslurp（咕噜）soup？Doyoupopbubblegum？Ifyoudo，yourhabitswon'thelpyouwinfriends-butthey'refun．Buthowaboutknuckle-popping？Notyoudoesthishobbygivepeoplearoundyouthe"】
Knuckle-popping（指关节砰砰响）
Do you slurp（咕噜）soup？Do you pop bubble gum？If you do，your habits won't help you win friends-but they're fun．But how about knuckle-popping？Not you does this hobby give people around you the"willies（[俚]神经紧张），"but cracking knuckles can lead to monster knuckles（异乎寻常的响声），and maybe-to arthritis （关节炎）．
At least，most people think knuckle-popping is bad．Well，there's no doubt that the people who have to listen to knuckles being snapped（啪地一声折断）can't stand the sound．But how bad is it for the knuckle-popper？
A doctor has looked into this indoor sport．He says it's not harmful．Dr．Robert L．Swezey found that his son was cracking his knuckles．And the kid's grandmother thought it was terrible．So Dr．Swezey went to a home for the aged．He studied the knuckles of old people there．Only one out of fifteen old people who said they cracked their knuckles all their lives had something wrong with their finger joints．Also，five out of twelve women who never cracked their knuckles had trouble with their joints．So if you want to go on popping your knuckles，Dr．Swezey says if OK，even if his son's grandma still doesn't like it．
28．People who hear others cracking their knuckles___．
A．are bothered．
B．don't notice the sound
C．start to crack their own knuckles．
D．feel it's as had as slurping soup．
29．When Dr．Swezey went to the old-age-home，what did he find out about old people who had cracked their knuckles？___
A．Only one old people had something wrong with their finger joins．
B．Only old women had cracked their knuckles．
C．About 6.7percent of the old people had something wrong with their finger joints．
D．The old people were all well．
30．Which of the following is right？___
A．Slurping soup and popping bubble gum are food habits．
B．Cracking knuckles will lead to arthritis．
C．No one likes cracking his knuckles．