介绍： 原文：The report includes both indoor and outdoor air pollution. Indoor pollution, which includes sources like home heating and cooking, has remained constant over the past several decades.

constant: happening all the time or repeatedly

Eg: constant interruptions

constant: that does not change(fixed)

介绍： 原文：The report includes both indoor and outdoor air pollution. Indoor pollution, which includes sources like home heating and cooking, has remained constant over the past several decades.

constant: happening all the time or repeatedly

Eg: constant interruptions

constant: that does not change(fixed)