detailed solution

Correct option is C

• Concept: The words which tell about the times an action is taking place are called adverbs of frequency, basically frequency of adverb informs us about how many times any incident takes place.
• They are categorised under adverb of time and which is written between the main verb or helping verb.
• 'Sometimes' is a adverb of frequency which will be used before the main verb.
• So the correct sentence is 'He sometimes plays soccer on Sunday.'
• Hence, option C is the correct answer.