Answer:
Hydrothermal vents
Step-by-step explanation:
A hydrothermal vent is found along with areas of volcanic activity in the ocean floor which discharges geothermally heated water. Tectonic plates in such areas move apart at spreading centers and hotspots to form hydrothermal vent.
A hydrothermal vent ejects hot and often toxic, fluids and gases into the surrounding seawater when seawater meets magma.
Hence, the correct answer is "Hydrothermal vents".