Which option is correct for curve $a$ and $b$?
| Curve | Equation | Type of Curve |
| :--- | :--- | :--- |
| $a$ | ? | ? |
| $b$ | ? | ? |

• A
  $\frac{dN}{dt} = rN$ for $a$,$\frac{dN}{dt} = rN(\frac{N-K}{K})$ for $b$; Exponential curve for $a$,Logistic curve for $b$
• B
  $\frac{dN}{dt} = rN$ for $a$,$\frac{dN}{dt} = rN(\frac{K-N}{K})$ for $b$; Exponential curve for $a$,Logistic curve for $b$
• C
  $\frac{dN}{dt} = rN$ for $a$,$\frac{dN}{dt} = rN(\frac{K-N}{K})$ for $b$; $S$-shaped curve for $a$,$J$-shaped curve for $b$
• D
  Both $(b)$ and $(c)$