Option D — Land left without cultivation for one agricultural year (or less than one agricultural year) is called current fallow land.
The textbook (Land Utilisation section) clearly defines current fallow as land "left without cultivation for one or less than one agricultural year." Examiners expect the exact definition; do not confuse it with "other than current fallow" (1–5 years) or "culturable waste land" (more than 5 years).