According to Greek philosophers, the smallest particle of matter that could not be further subdivided was called

The correct answer is (b) atom. According to Greek philosophers, especially Democritus, the smallest particle of matter that could not be further divided was called the “atom” (from the Greek word “atomos,” meaning indivisible). Modern science later refined this concept.
Class 9th Science NCERT MCQ Questions
NCERT Books MCQ Questions Session 2024-2025.