The question refers to the area where the density, or concentration, of cattle population per 100 hectares of gross cropped area is the highest.

Option 1, Bihar, is incorrect as although Bihar has a significant amount of cattle, it doesn`t rank the highest when factoring in the size of its gross cropped area.

Option 2, Haryana, is the correct answer. This is because Haryana, despite being smaller than other states, has a strong pastoral and agricultural tradition leading to higher cattle densities per 100 hectares of cropped area.

Option 3, Madhya Pradesh, is incorrect. It`s a large state with significant cattle populations, however, the size of the state means the density of cattle per 100 hectares of gross cropped area is not as high as in Haryana.

Option 4, Uttar Pradesh, is incorrect despite it being a state with one of the highest absolute numbers of cattle. The density is lower due to its large gross cropped area.

The correct answer thus reflects the balance between cattle populations and the size of the cropped area in each state.