Use Pythagorean theorem!!! Will give b !!

Answer:
The last one
Step-by-step explanation:
Hey There!
The Pythagorean Theorem states that
the two legs squared added together equal the hypotenuse square
we are given the two legs so to find the missing side we square them, then add them together
[tex]1^2=1\\3^2=9\\9+1=10[/tex]
the missing side length equals
[tex]\sqrt{10}[/tex]
hope this helps!