Snakes are included under which category in a food chain?

Whale is

Herbivores are called

Which of the following is a producer in the plant kingdom?

Arrange the stages of hydrarch succession in the correct sequence.

Read the following statements carefully and answer the question:
$(1)$ Pyramids of number and biomass can be upright or inverted in an ecosystem.
$(2)$ Phosphorus and sulfur are sedimentary cycles.
$(3)$ The largest reservoir of carbon on Earth is found in the oceans.
$(4)$ The structural and functional unit of ecology is the ecosystem.
Which of the above statements are correct?