A Fleet of Rental Cars - All the Same Make $24.1$

A fleet of rental cars - all the same make, model, and year - has a mean fuel efficiency of $24.1$ miles per gallon (mpg) . A random sample of 45 cars are selected and the air filter of each is replaced with a new one. Let $\mu$ be the population mean fuel efficiency score that would occur if every car's air filter were replaced. The air filter change is deemed effective if $\mu > 24.1 \mathrm { mpg }$ . A test is made of $H _ { 0 } : \mu = 24.1$ versus $H _ { 1 } : \mu > 24.1$ . Consider these possible conclusions:
i) . The air filter changes are effective.
ii) . The air filter changes are not effective.
iii) . The air filter changes might not be successful.
Which of the three conclusions is best if $H _ { 0 }$ is rejected?

A) iii
B) ii
C) $\mathrm { i }$