Final answer:
The expression 4.3 x 10^-4 is less than 4.32 x 10^-4 because when comparing the decimal parts, 4.3 is less than 4.32.
Step-by-step explanation:
To compare the two expressions 4.3 x 10^-4 and 4.32 x 10^-4, we look at the significant digits of each expression. Since they both have the same exponent part (-4), the comparison comes down to the decimal part. We can see that 4.3 (which is the same as 4.30 when considering significant figures) is less than 4.32. So, the proper comparison is:
4.3 x 10^-4 < 4.32 x 10^-4
Therefore, the correct answer is:
B. 4.3 x 10^-4 < 4.32 x 10^-4