Concept:Some ecological factors act on every type of habitat, while others, like humidity, are specific to certain environments only.
Explanation:Temperature, light, and pressure affect both terrestrial and aquatic habitats.
Humidity is the amount of water vapour present in the air.
Aquatic habitats are fully submerged in water, so air humidity has no direct effect on the organisms living there.
Therefore, humidity does not affect all habitats.
Answer:B. humidity