Step 1: Recall what plantation farming means.
It involves growing a single crop on a large scale with heavy investment, usually for commercial and industrial use rather than daily food.
Step 2: Sort the given crops.
Wheat, bajra and rice are food grains grown as staple cereals, not plantation crops.
Step 3: Identify the plantation crop.
Rubber is grown on large estates in hot, humid areas like Kerala, Tamil Nadu and Karnataka, which makes it the plantation crop here.
Hence, the correct answer is option (D) Rubber.