What are NPK fertilizers, adverse effects of over-fertilization, domestic animals, autotrophs, and herbivores?

Here are the answers to the questions:

29. What chemical elements are present in NPK fertilizers?
The correct option is D.
NPK fertilizers contain the primary macronutrients: Nitrogen (N), Phosphorus (P), and Potassium (K).
The final answer is $\boxed{\text{D. Nitrogen, phosphorus, potassium}}$

30. Which of the following is not an adverse effect of applying too much chemical fertilizers on the environment?
The correct option is D.
While fertilizers are designed to increase soil fertility, applying too much can lead to adverse effects like decreased long-term soil fertility, increased soil acidity, and destruction of soil structure. Therefore, "increases soil fertility" is the intended positive effect, not an adverse one.
The final answer is $\boxed{\text{D. Increases soil fertility}}$

31. Which one is a domestic animal?
The correct option is C.
Cattle are domesticated animals raised for products like milk, meat, and leather, or for labor.
The final answer is $\boxed{\text{C. Cattle}}$

32. Which of these is an example of autotroph?
The correct option is C.
An autotroph is an organism that produces its own food, typically through photosynthesis. Plants are primary examples of autotrophs.
The final answer is $\boxed{\text{C. Plants}}$

33. Animals that feed on only plants are known as
The correct option is D.
Herbivores are animals whose primary food source is plant-based.
The final answer is $\boxed{\text{D. Herbivores}}$

34. An example of an omnivore is
The correct option is A.
An omnivore is an animal that eats both plants and animals. Humans (Man) are omnivores.
The final answer is $\boxed{\text{A. Man}}$