Answer:
The correct answer is - mutualistic.
Explanation:
The symbiosis or relationship between the bacterium xenorhabdus namtophilia and Steinernema carpocapsae, the nematode host is known as mutualistic or the cooperation in between them. Both the organisms live in a symbiosis in which both are benefited.
The nematode lives free till the early infective juvenile stage only. Bacterium present in both conditions as individual and with the symbiosis of the host.
Thus, the correct answer is - mutualistic.