C(t) = P(1+r)^t
A) is WRONG: since the population is INCREASING, then r > 0
B) is incomplete: since the value of C depends ALSO on r (that is missing)
C) is Wrong: since only r is a percentage and NOT 1+r
D) WRIGHT: Prove:
C(t) = P(1+r)^t if t = 0 then C₀ = P(1+r)⁰ or
any number with zero exponent is EQUAL to 1, so
C₀ = P(1+r)⁰ → C₀ = P(1) = P
