Ans. (A). Commensalism because one species benefits.
A biological association between two organisms, in which one organism gets benefit, while other organism gets neither harm nor benefit, is known as commensalism.
As in given association, man-of-war fish is getting benefit from Physalia physalis fish as this interaction provides shelter to man-of-war fish, but Physalia physalis is not affected by this interaction as it does get any benefit or harm. Hence, this relationship shows commensalism.
Thus, the correct answer is option (A).
