Ecologists wanted to estimate the mean biomass (amount of vegetation) of a certain forested region. The ecologists divided the region into plots measuring 1 square meter each, and they selected a random sample of 9 plots. The mean biomass of the 9 plots was 4.3 kilograms per square meter and the standard deviation was 1.5 kg/m^2. Assuming all conditions for inference are met, which of the following is a 95% confidence interval for the population mean biomass, in kg/m^2?

a. 4.3 ± 1.96 (√ 1.5/3)
b. 4.3 ± 1.96 (1.5/3)
c. 4.3 ± 2.306 (√ 1.5/9)
d. 4.3 ± 2.306 (1.5/9)
e. 4.3 ± 2.306 (1.5/3)