The correct answer is option 4, which states that all three crop plants (banana, potato, and turmeric) are propagated by vegetative methods.

Propagation refers to the process of creating new plants from existing ones. Vegetative methods of propagation involve using plant parts such as stems, leaves, or roots to grow new plants, instead of relying on seeds.

Bananas are propagated through a process called suckering, where new shoots or suckers emerge from the base of the parent plant and are then separated to grow into new plants.

Potatoes are propagated through a method called vegetative propagation or cloning, where small sections of the tuber, known as seed potatoes, are planted to produce new plants.

Turmeric is propagated by dividing rhizomes, which are underground stems. The rhizomes are separated and planted to grow into new turmeric plants.

Therefore, all three crop plants listed in the question - banana, potato, and turmeric - can be propagated using vegetative methods.