Biological interactions are defined by sign conventions:

• Amensalism ($-/0$): One species is inhibited, harmed, or destroyed, while the other remains completely unaffected (e.g. Penicillium producing penicillin inhibiting bacteria, or large trees shading out smaller seedlings).
• Commensalism ($+/0$): One species benefits while the other is unaffected.
• Mutualism ($+/+$): Both interacting species benefit.
• Predation ($+/-$): The predator benefits while the prey is harmed/killed.
  
  Option analysis:
• Commensalism: $+/0$ interaction (one benefits, other neutral).
• Amensalism: Correct, $-/0$ interaction (one suffers, other neutral).
• Mutualism: $+/+$ interaction (both benefit).
• Predation: $+/-$ interaction (one benefits, other killed).

The Kyoto Protocol is an international treaty adopted in Kyoto, Japan, in December 1997 under the UNFCCC. It commits state parties to reduce greenhouse gas emissions ($CO_2, CH_4, N_2O$, HFCs, PFCs, and $SF_6$) to mitigate anthropogenic global warming. In contrast, the Montreal Protocol (1987) targets ozone-depleting substances, and the Stockholm Convention (2001) governs Persistent Organic Pollutants.

Option analysis:

• Greenhouse gases: Correct, the Kyoto Protocol explicitly sets binding targets for greenhouse gas emission reductions.
• Pesticide pollution: Governed by the Stockholm and Rotterdam Conventions.
• Water pollution: Governed by MARPOL, Ramsar, and regional seas treaties.
• Ozone depletion: Governed specifically by the Montreal Protocol (1987).

The Gulf Stream is an intense, swift western boundary warm ocean current in the western North Atlantic Ocean. Originating in the warm Gulf of Mexico, it flows through the Straits of Florida, hugs the eastern coast of the United States, and carries enormous quantities of tropical thermal energy northward across the Atlantic towards Western Europe as the North Atlantic Drift.

Option analysis:

• Cold water current: Examples include the Labrador Current, California Current, and Oyashio Current.
• Warm water current: Correct, the Gulf Stream is a premier western boundary warm current.
• Bottom current: Deep thermohaline currents like Antarctic Bottom Water.
• Inshore current: Local wave-driven rip or coastal longshore currents.

Paralytic Shellfish Poisoning (PSP) is caused by saxitoxin and its derivatives, produced by marine dinoflagellates (principally Alexandrium, Gymnodinium catenatum, and Pyrodinium bahamense). Saxitoxin selectively blocks voltage-gated sodium channels on nerve and muscle cell membranes, preventing action potential propagation and causing numbness, muscular paralysis, and respiratory failure.

Option analysis:

• Saxitoxin: Correct, neurotoxin causing Paralytic Shellfish Poisoning (PSP).
• Brevetoxin: Produced by Karenia brevis, causes Neurotoxic Shellfish Poisoning (NSP).
• Okadaic acid: Produced by Dinophysis, causes Diarrhetic Shellfish Poisoning (DSP).
• Domoic acid: Produced by Pseudo-nitzschia, causes Amnesic Shellfish Poisoning (ASP).