To check the bigger or smaller number, we can adjust the numbers such that they both have the same exponential power.
The first number can be written as shown below:
[tex]4.3\times10^6=4.3\times10\times10^5=43\times10^5[/tex]Now, both numbers have the same exponent. Therefore, we can compare the numbers 43 and 12.1.
Observation of the numbers on the number line shows that:
[tex]43>12.1[/tex]Therefore, we have that:
[tex]43\times10^5>12.1\times10^5[/tex]The correct option is OPTION A.