Which of the following pairs is correctly matched?

The correct answer is Option (3) → Aquarium – Man-made ecosystem

Ecosystems are grouped into two basic kinds: terrestrial (on land) and aquatic (in water). Some ecosystems are made and kept by people; NCERT calls crop fields and an aquarium man-made ecosystems.

Option (1) Estuary – Terrestrial ecosystem — Incorrect. An estuary is an aquatic ecosystem, like a pond, lake, wetland or river.

Option (2) Crop field – Natural terrestrial ecosystem — Incorrect. A crop field is raised and kept by people, so it is a man-made ecosystem, not a natural one.

Option (3) Aquarium – Man-made ecosystem — Correct. An aquarium is set up and kept by people, so it is a man-made ecosystem.

Option (4) Wetland – Terrestrial ecosystem — Incorrect. A wetland is an aquatic ecosystem. Forest, grassland and desert are the terrestrial examples.

NCERT Extract:
Ecosystem – “… Since this system is too much big and complex to be studied at one time, it is convenient to divide it into two basic categories, namely terrestrial and aquatic. Forest, grassland and desert are some examples of terrestrial ecosystems; pond, lake, wetland, river and estuary are some examples of aquatic ecosystems. Crop fields and an aquarium may also be considered as man-made ecosystems.”