Choose the appropriate noun form to complete the sentence. He is planning to…

Answer: The correct phrase is "politics next year."

Why "politics" is correct:

• "Politics" here is a noun that refers to political activities, the profession, or the field; it is used without an article in this context (a mass/uncountable use).

• "Next year" is the natural time phrase to place after the activity. "By the next year" is awkward; "by next year" or "next year" are preferred.

Why the other choices are incorrect:

• "political by the next year": "political" is an adjective, not a noun, so it cannot complete "retire from ..."

• "politic the next year": "politic" is also an adjective (meaning prudent); it is not a noun and does not fit the required structure.

• "politician next years": "politician" denotes a person (a countable noun) and would need an article or pluralization, and "next years" is ungrammatical here. This does not convey the intended meaning of leaving the field of politics.

Correct sentence: He is planning to retire from politics next year.