It's either the first answer or the third, here's my reasoning.
For the rhyming of I and dry, it creates a soft like tone and stands out as a rhyme. However, the number of words in each line of the stanza show the true rhythm of the poem as it is not only depicted in literally how the lines are aligned but the amount.
Therefore, if I had to choose an answer, I would choose the third option.
Invisible strength could mean a hidden talent. Or strength (strength to do something challenging, out of their comfort zone) the character didn't know they had.
