题目

Flying cars may soon become a ___41___    (real). The rideshare service Uber has asked ___42___ expert from NASA, the American space agency, ___43___    (help) the company develop cars that can fly. Uber plans to use flying vehicles ___44___ the future to avoid traffic in and around cities. The company wants to use small, totally electric aircraft, ___45___ could take off and land like a helicopter on top of parking garages. Uber said its flying vehicles would be much ___46___ (quiet), cost less to operate and produce less pollution than helicopters. One person in San Francisco t℃时，某硝酸钾溶液100g，恒温蒸发掉10g水，析出了2g晶体，再恒温蒸发掉10g水，又析出了4g晶体，则在t℃时，原来100g溶液是________（饱和、不饱和）溶液，硝酸钾在t℃时的溶解度为________g．