In Anapestic meter, each foot has two unstressed syllables followed by a stressed syllable. "And so he plays" has stressed syllables right after the first word. Trochaic would demand that the first syllable was stressed. And irregular is just not the case since it has a pattern of unstressed and stressed syllables.
The pattern is as it follows:
The iamb, which in English indicates an unstressed syllable followed by a stressed syllable; and "pentameter": it's always made with 10 syllables.
The correct answer is:
C, iambic pentameter