Which rational expression is in simplified form?
a. (x^2-x-6)/(x^2+"3x+"2)
b. (x^2+6x+8)/(x^2+2x-3)
c. (x^2-6x+9)/(x^2-2x-3)
d. (x^2+3x-4)/(x^2+x-2)

Ur environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 4.04.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 2525 samples is 4.44.4 ppm with a standard deviation of 0.80.8. assume the population is normally distributed. a level of significance of 0.020.02 will be used. make the decision to reject or fail to reject the null hypothesis. answer tables