Please someone help I can’t this

Answer:
When i took it i chose C and was right. I'm not sure if we use the same school but it was my answer. Hope it helps.
Step-by-step explanation:
Answer:
c
Step-by-step explanation:
[tex] {a}^{2} = {c}^{2} - {b}^{2} [/tex]
a^2=25-9
a^2=16
a=4