Which one of the following is not an example of terrestrial ecosystem?

The correct answer is Option (3) → Estuaries

Option (1) Forest — Terrestrial.

Option (2) Grassland — Terrestrial.

Option (3) Estuaries — Not terrestrial. Estuaries are aquatic ecosystems where rivers meet the sea.

Option (4) Deserts — Terrestrial.

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.”