Q.The interaction in nature, where one gets benefit on the expense of other is...

Step 1. The question describes an interaction where one organism gains benefit while the other suffers at its expense.

Step 2. Among the four given options, check each against its plus/minus scoring: Mutualism is (+, +) — both benefit, nobody loses; Amensalism is (--, 0) — one is harmed but the other gains nothing; Commensalism is (+, 0) — one benefits, the other is simply unaffected; Predation is (+, --) — the predator directly benefits while the prey is directly harmed (killed and consumed).

Step 3. Only predation matches 'one gets benefit on the expense of other' exactly, since it is the only listed option where one party's gain is causally tied to the other party's loss.

Compare each option's plus/minus/zero scoring against the description 'benefit at the expense of the other' and pick the only exact match.

• Picking Amensalism, which harms one side but gives no benefit to the other, rather than a benefit-at-a-cost relationship.
• Overlooking that Parasitism also fits this description but is not offered as an option here.