If Arrivals Occur According to the Poisson Distribution Every 20 $\lambda$

Multiple Choice

If arrivals occur according to the Poisson distribution every 20 minutes, then which is NOT true?

A) $\lambda$ = 20 arrivals per hour
B) $\lambda$ = 3 arrivals per hour
C) $\lambda$ = 1/20 arrivals per minute
D) $\lambda$ = 72 arrivals per day