Final answer:
The best statement of a possible theme in the poem 'The Dolphin' is 'Wild creatures are miserable in captivity,' and the poet's word choice, contrasting terms of confinement with those of freedom, supports this theme.
Step-by-step explanation:
Part A of the question asks for the best statement of a possible theme in the poem 'The Dolphin.' Given the context of the poem that discusses captivity and a longing for freedom, Option A, 'Wild creatures are miserable in captivity', seems the most plausible. The dolphin is described as trapped and confined, which implies misery in captivity. For Part B, regarding how the poet's word choice helps convey the theme identified in Part A, the answer is Option D. Words such as 'trapped', 'circle round and round', and 'not to roam' create a stark contrast to words like 'roam' and 'leap', which evoke images of freedom. This contrast highlights both the captivity of the dolphin and the yearning for a different, freer existence.