The correct answer is option 1: Rajasthan.

Plantation agriculture refers to the large-scale commercial farming of crops such as tea, coffee, rubber, and spices. This type of agriculture requires specific climate and soil conditions, which may not be suitable in certain regions.

Rajasthan is a state located in the northwest part of India. It is known for its arid and desert-like conditions, with a scarcity of water resources. These conditions are not favorable for the cultivation of plantation crops, making Rajasthan not prominent for plantation agriculture.

Option 2, Assam, is known for its production of tea. The state`s climate and soil are well-suited for growing tea plantations.

Option 3, Nagaland, produces crops like coffee, cardamom, and ginger. Its climate and suitable terrains make it suitable for plantation agriculture.

Option 4, Kerala, is known for its production of spices like pepper, cardamom, and cinnamon. The state has a humid climate and fertile soil, making it ideal for plantation agriculture.

In conclusion, while options 2, 3, and 4 are prominent for plantation agriculture, option 1, Rajasthan, is not known for this type of farming due to its arid conditions and water scarcity.