Which grade of tire is providing better quality? explain. choose the correct answer below. a. grade y provides the better quality. while the mean of grade x is closer to the expected mean, the standard deviation of grade y is much smaller. b. grade x provides the better quality. while the mean of grade y is closer to the expected mean, the standard deviation of grade x is much smaller. c. grade y provides better quality because its mean is much smaller. d. grade x provides better quality because its mean is much smaller.