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     Space travel is definitely bad for astronauts' bones, reducing their bone density(密度)

after only a month of weightlessness, according to French research published on Friday.

     Laurence Vico and his fellow workers at St Etienne University called for more research

into the effects of microgravity, after their study of 15 astronauts from the Russian MIR station

showed bone loss continued throughout space flights.

     "Bone loss was especially striking in four astronauts, " the scientists reported in the Lancet

Medical Journal.

     They measured the bone mineral density (BMD) of bones in the forearm(前臂) and

lower leg of the astronauts who had spent one to six months in space.

     The BMD loss was significant in the tibia(胫骨) of the lower leg, a weight-bearing bone,

but barely changed in the radius(桡骨) of the forearm. "Our results indicate the need to

investigate not only different bones, but also different areas of the same bone since not all

sites of the skeleton (骨架) are similarly affected by space conditions, " they added.

     Without gravity the body isn't bearing any weight so there is no need for calcium (钙)

which makes bones strong, and it becomes empty into the bloodstream.

     The research team suggested in future scientists should try to determine if the loss of bone

density was only on weight-bearing bones on longer flights, also the possible recovery after

returning to Earth.

1. French scientists did their research on Russian astronauts, because _______.

A. they only cared for the Russian astronauts

B. they were not interested in their own astronauts

C. the Russian government invited them to do their research

D. the Russian astronauts worked in space for a period of time

2. Scientists have found that _______.

A. the BMD loss may cause serious illness to astronauts

B. the BMD loss may cause some change in astronauts' bodies

C. astronauts shouldn't care about the BMD loss

D. astronauts should take some calcium before space travel

3. What cause the BMD loss to astronauts, according to this passage?

A. The food they eat in space.

B. The drinks they take in space.

C. The temperature in space.

D. The gravity in space.

4. In the third paragraph, the underlined word "striking" means ______.

A. unusual

B. simple

C. weak

D. slow