True estuarine organisms can tolerate the salinity between:

Correct option is C

Correct Answer: (c) 5–30 ppt
Explanation:
→ True estuarine organisms are adapted to wide but moderate salinity fluctuations, commonly in the 5–30 ppt range found across upper to middle estuary zones.
→ They show physiological tolerance to daily/seasonal salinity changes.
Information Booster:
→ Organisms narrower in tolerance are oligohaline (<5 ppt) or euryhaline if tolerating even higher ranges.
Additional Information (Other Options):
(a),(b),(d): narrower or excessively broad ranges compared with the typical true-estuarine band.