The following questions are multiple choice questions about biology and ecology. Please provide the answers and explanations for each.

Here are the answers to the questions:

35. A natural environment in which a particular species of organism lives is
The correct option is C.
A habitat is the natural environment where an organism lives and finds everything it needs to survive.
The final answer is $\boxed{\text{C. Habitat}}$

36. ..................................... refers to trees as the natural home of living organism
The correct option is D.
Arboreal habitat refers to an environment where organisms primarily live in trees.
The final answer is $\boxed{\text{D. Arboreal habitat}}$

37. Which of these organisms live in water?
The correct option is B.
Tadpoles are the larval stage of frogs and toads, and they live entirely in water.
The final answer is $\boxed{\text{B. Tadpoles}}$

38. An example of a decomposer is
The correct option is B.
An earthworm is a decomposer, breaking down dead organic matter and returning nutrients to the soil.
The final answer is $\boxed{\text{B. Earthworm}}$

39. The system of farming in which the same crop is grown on the same piece of land from year to year is called
The correct option is A.
Monocropping (or monoculture) is the agricultural practice of growing a single crop year after year on the same land.
The final answer is $\boxed{\text{A. Monocropping}}$

40. Which of the following is a legume?
The correct option is D.
A cowpea is a type of bean and is classified as a legume. Legumes are plants that have pods containing seeds.
The final answer is $\boxed{\text{D. Cowpea}}$