Answer:
Option (1).
Explanation:
Statement given states that "A canary's beak is, at most 20 mm long."
Word "at most" means "the maximum".
So at most length of the beak means "length of the beak is less than equal to 20 mm".
And the expression representing this statement algebraically will be,
x ≤ 20
Therefore, option (1) will be the correct option.