The term 'sinewy' most closely means:
A. Athletic.
As a dictionary can show you, the word 'sinewy' is an adjective with the meaning of "consisting of or resembling sinews; with strong muscles and little fat". One synonymous for 'sinewy' is 'athletic'.
I would say that the adjectival phrase is B. overly excited. An adjective describes a noun, so an adjectival phrase would be a phrase that describes a noun. "overly excited" describes the noun "children." "to the front" and "of the room" are prepositional phrases and "pushed" is a verb.
