2006年7月1日，青藏铁路正式通车，许多旅客乘车穿越青藏高原时，会发生高原反应，感到呼吸困难，这是因为高原地区空气里

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A．氧气体积分数大大低于21%

B．氮气体积分数大大超过78%

C．氧气体积分数仍约为21%，但空气稀薄

D．CO₂气体含量大大增多

Object-oriented DBMS integrated a variety of (81) data types-such as business procedures, graphics, pictures, voice and annotated text.
Object orientation also makes a (82) to application development efficiency. It makes the data, functions, attributes, and relationships an integral part of the (83) . In this way, objects can be reused and replicated.
Some leading RDBMS vendors support the concept of integrating object management capabilities with their current line of relational products. That capability enable users to the development cycle, since integrity logic and business roles no longer need to be programmed (84) each application.

A．tool

B．in

C．idea

D．contribution

E．joke

F．short

G．object

H．theoretical

I．extent

J．shorten K. real-world L. into