题目内容：
Questionsare based on the following passage． Getting out of a pricey monthly gym membership has traditionally been as hard as squeezing intolycra (莱卡) after the Christmas holiday．But at Fitness4Less, a low-cost gym in east London, membershipis more flexible．Customers pay 15．99 a month and can leave at any point．Like low-cost airlines andsupermarkets, budget gyms are muscling in on the market．
Their rise reflects the recent shakiness of Britain's economy．Although budget chains constitute only 8%of the revenue, they now account for 21% of all fitness-club (健身俱乐部) members．Low-cost gyms boastaround 5,000 members per club compared with an industry average of about 1,900, according to Mintel, aconsultancy (咨询公司)．Such high numbers help keep membership cheap．Many accommodate such largenumbers by opening 24 hours a day．That is appealing to the growing numbers of people doing shift work．
Membership turnover (流动率) is high, too, but two-thirds of those who leave Fitness4Less come back,says Emma Edwards, one of its owners．Budget gyms are growing faster than any other part of the sector;roughly 200% since 2011．Pure Gym, a low-cost chain, has opened 75 clubs since 2009．Fitness First, a mid-range chain where monthly membership can cost 70, only has 75 clubs now, down from 150 in 2007．
Budget-gym members scan their fingerprints or use personal ID numbers to gain access．That cutsspending on costly membership cards and receptionists．There are few decorations, such as saunas and cafes．Up to 70% of the machines at The Gym, another fast-growing chain, use no electricity, reducing overheads．No contracts mean no salaries or commissions for salespeople．
Other cheap ways to keep fit are thriving too, from online classes to low-cost mobile fitness apps．Fancygyms——where single classes can cost more than a monthly budget gym membership——are also flourishing．Itis just the fatter middle that is being squeezed．
What does the author say about traditional gym? A．They have been always kept plenty of members．
B．It is difficult to put on their lycra costume of member．
C．They have marketing mode that is similar to airlines and supermarkets．
D．You cannot get it out at random once join in．
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