The correct answer is option 4, fungi.

Fungi are non-green heterotrophic organisms that belong to the plant kingdom. They are not classified as plants because they lack chlorophyll, which is necessary for photosynthesis. Instead, fungi obtain nutrients by decomposing organic matter or by forming mutualistic relationships with other organisms.

Option 1, mosses, is not the correct answer as mosses are green plants called bryophytes. They have chlorophyll and can perform photosynthesis.

Option 2, ferns, is also not the correct answer as ferns are also green plants called pteridophytes. Like mosses, they have chlorophyll and can perform photosynthesis.

Option 3, algae, is also not the correct answer as some algae are green plants and can perform photosynthesis. However, there are other types of algae that can be heterotrophic, but they are not considered part of the plant kingdom.

Therefore, the correct non-green heterotrophic plants of the plant kingdom are fungi.