Final answer:
The suffix -ism in the word realism means 'belief of' or 'the practice of,' indicating an ideology, movement, or belief system.
Step-by-step explanation:
The suffix -ism, as used in the word realism, most nearly means 'belief in' or 'the practice of'. Therefore, the answer is c. belief of.
This suffix is common in English and is used to form nouns that either describe a certain ideology or belief system, or denote a movement in arts or philosophy associated with a specific doctrine or practice.
Examples include realism, which refers to a belief in representing subjects as they are, as opposed to idealistically; and structural realism, indicating a belief in or adherence to the principles of a particular structural approach.