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参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】Passage Four Initial voyages into space introduced questions scientists had never before considered. Could an astronaut swallow food in zero gravity To keep things simple, astronauts on the Project ...
A.
was an unusual problem among astronauts
B.
was what puzzled the early scientists
C.
caused new problems in space flights
D.
drew the attention of the general public
【单选题】Initial voyages into space introduced questions scientists had never before considered. Could an astronaut swallow food in zero gravity To keep things simple, astronauts on the Project Mercury ate foo...
A.
the variety of food options in space
B.
the dietary need of astronauts in space
C.
the problems of living in the space station
D.
the improvement of food offered in space