Growth rate of bacteria is given by the following equation:-
![y = a. {r}^(x)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/5jea1w5kfmfwafx69jxxu3f4jwvju1hp3e.png)
where y is the final population, a is the initial population, r is the growth rate, and x is the time.
![given \: \: y = 280 * {2}^(x)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/zb7mbkh3csjqmoe1at23xjk08vg61w9zqw.png)
So initial population is 280, and growth rate is 2.
Hence, option C i.e. 2 is the final answer.