空气的净化问题正日益受到人们的关注．下列各组成分均属于空气污染物的一组是  [ ]

A．SO₂ CO  NO₂  

B．CO₂ HCl  N₂  

C．CH₄ CO₂ H₂  

D．SO₂ N₂ O₂

A typical (160) language contains an applicative sub-language which approximates the mathematical abstractions of "timeless" functions applied to "spaceless" values, where the actual operation sequences and use of storage space during expression evaluation are organized behind the (161) . In this setting, values are data structures of low volume, typically a few computer words or less, which means that an illusion of spacelessness can be realized by having (162) results during expression evaluation stored at the discretion of the language implementation, and effecting parameter (163) and (164) operations through value copying.

（164）是（）

A.assignment

B.design

C.value

D.dispatch