The Decay Rate of a Radioactive Sample Is Defined as the Number

The decay rate of a radioactive sample is defined as the number of decays per second. For a sample with N particles and a decay constant $\lambda$ , the decay rate is

A) proportional to $\lambda$ and inversely proportional to N.
B) proportional to $\lambda$ but independent of N.
C) directly proportional to both $\lambda$ and N.
D) independent of $\lambda$ but proportional to N.
E) inversely proportional to both $\lambda$ and N.