The underlined words in the lines illustrate the use of assonance. Assonance is the “relatively close juxtaposition of similar sounds especially of vowels” and the “repetition of vowels without repetition of consonants (as in stony and holy) used as an alternative to rhyme in verse”. It is also defined as the “resemblance of sound in words or syllables”. In these lines, the "o" sound in "along," "strong," and "song" is repeated, demonstrating assonance.