**Core Concept**
The amount of air that can be inhaled above tidal volume by maximum inspiratory effort is a measure of lung function, specifically the inspiratory capacity. Inspiratory capacity (IC) is the amount of air that can be inhaled from the resting expiratory level to the maximum inspiratory level. This is an important concept in respiratory physiology.

**Why the Correct Answer is Right**
The inspiratory capacity is determined by the volume of the lungs and the chest wall, as well as the strength and coordination of the respiratory muscles. The inspiratory capacity can be increased by increasing the volume of the lungs, which can be achieved by increasing the lung volume or by increasing the chest wall volume. The maximum inspiratory effort is the maximum effort a person can make to inhale air, and it is typically measured during a spirometry test.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the amount of air that can be inhaled above tidal volume by maximum inspiratory effort.
**Option B:** This option is incorrect because it refers to the residual volume, which is the amount of air left in the lungs after a maximal exhalation.
**Option C:** This option is incorrect because it refers to the functional residual capacity, which is the amount of air left in the lungs at the end of a passive exhalation.

**Clinical Pearl / High-Yield Fact**
The inspiratory capacity is an important measure of lung function, and it can be used to diagnose and monitor respiratory diseases such as chronic obstructive pulmonary disease (COPD) and asthma.

**Correct Answer:** D. Inspiratory Reserve Volume (IRV).