Ambient air quality standard – UGC NET Question

An ambient air quality standard specifies the maximum acceptable concentration of a pollutant in outdoor air over a defined time period. These standards are set to protect human health and the environment. The stem clearly refers to such permissible limits,so standard is the correct word.

Option A:
An inventory is a detailed list or accounting of emission sources and quantities. While useful for management,it does not itself state permissible limits or health based thresholds. Hence it is not suitable for the blank.

Option B:
A standard is a legally or administratively established benchmark against which actual air quality is compared. Ambient air quality standards guide regulatory action and monitoring. This is exactly what the stem describes,so this option is accurate.

Option C:
A profile usually means a descriptive representation of air quality conditions or emissions but does not inherently define acceptable limits. Therefore it is not equivalent to the concept in the question.

Option D:
A budget in environmental science may refer to the balance of emissions and removals of a pollutant or greenhouse gas. It is different from health based concentration limits,so it cannot fit the blank.