For an A.P. if a25 - a20 = 45, then d equals to:

Answer: Option A

a_n = a + (n - 1) × d
⇒ a₂₅ = a + 24d
and a₂₀ = a + 19d
a₂₅ - a₂₀ = 45
⇒ a + 24d - a - 19d = 45
⇒ 5d = 45
⇒ d = 9