Answer:
The metrical foot Carroll uses in the poem is ANAPESTIC.
Step-by-step explanation:
The metrical foot Lewis Carroll uses in the "You Are Old, Father William" poem is ANAPESTIC. Anapest is a poetic device defined as a metrical foot of three syllables in a line of a poem wherein the first two syllables are short and unstressed, followed by a third syllable that is long in quantitative meter and stressed in accentual meter.