Step 1: Concept:
Two clues are given: standards are voluntary, and they are reviewed every five years. We look for the body that matches both clues.
Step 2: Clue one: voluntary:
Legal bodies such as FSSAI make rules that must be followed. WTO is about trade agreements. So the voluntary clue removes FSSAI and weakens WTO.
Step 3: Clue two: five year review:
ISO runs a regular review of each standard, about every five years, to decide whether to keep, revise or withdraw it. This is a well known ISO practice.
Step 4: Reading the passage:
In the passage, the sentence about voluntary adoption comes just after the ISO mission is explained. It refers to the standards of the ISO.
Step 5: Why not Codex:
Codex texts are offered as guidance for countries, but the question pairs the voluntary adoption line and the review cycle with ISO in the passage. So the better match is ISO.
Step 6: Final check:
FSSAI sets binding rules in India, WTO runs trade agreements, and Codex is a source of guidance for national rules. Only ISO is described as a federation of national standards bodies whose standards are taken up by choice and then reviewed again after five years. All clues therefore meet at option 4.
Final Answer:
Both clues point to ISO, so option 4 is the answer.
\[ \boxed{4} \]
