The difference in population of Bacteria A and Bacteria B after 4 days is what we are after.
Population of Bacteria A is modelled as follows
[tex]\begin{gathered} f(t)=5\times4^t \\ \text{where t = time in days} \\ f(t)=5\times4^4 \\ f(t)=5\times\text{ }256 \\ f(t)=1280 \end{gathered}[/tex]Population of Bacteria B is modelled as follows
[tex]\begin{gathered} g(t)=10\times2^t \\ g(t)=10\times2^4 \\ g(t)=10\times16 \\ g(t)=160 \end{gathered}[/tex]The answer is D . The population of bacteria A is 8 times greater than bacteria B.