Destruction of the bacteria is 4 hours from now for us to find answers to the question asked we need to know either of these 2 things;
(a) The number of cell i.e the size of the population either now or at any given point in time
(b) The period of doubling and the size of the constant interval.

Statement 1
The population just divided and since the population divide two hours ago, the population has quadrupled increasing by 3750 cells.
Since the division two hours ago and the division just now the population has quadrupled {4 times} that is about two doubling periods
and this means each doubling period has a constant interval of 1 hour.
Thus in the next 2 hours, the population would have quadrupled again and at the end of 2 hours 3750 will be 3 times what it was 2 hours ago,
hence
The statement alone is SUFFICIENT

Statement 2
The population will double to 40000 cells with one hour remaining until the scientist destroys the sample .
This statement tells us about the population at a point in time, but there is no information about the doubling period and the constant interval
hence statement 2 is is INSUFFICIENT.
$$answer\ is\ optionA$$