Iffis the prob. density function of a continuous random variable X, then

∫(from x to infinity) f(t) dt equals:

a. P(X ≤ x)

b. P(X ≥ x)

c. P(X ≥ t)

d. P(X = x)

e. P(X = t)

I picked B, Im pretty sure about this, but i really do not understand why. can someone help explain to me? thank you