Help me with the answer please

11. a particular type of cell doubles in number every hour. which function can be used to find the number of cells present at the end of h hours if there are initially 4 of these cells? a. n = 4 ()" b. n = 4(2)" c. n = 4 + (2)" din = 4 +"

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Can someone answer this question for me