A cosmetics company decides to compare its new nail polish product, Bella, with three other nail polish brands: Primrose, Shine, and Glo. In an experiment, participants are divided into four groups. Each group of women is asked to wear nail polish from one of the four brands. The results for Primrose, Shine, and Glo are compared with those for Bella, and a conclusion is drawn. What does the type of nail polish represent in this case?

A. the control group
B. the explanatory variable
C. the response group
D. the response variable

According to a research study, parents with young children slept 6.4 hours each night last year, on average. a random sample of 18 parents with young children was surveyed and the mean amount of time per night each parent slept was 6.8. this data has a sample standard deviation of 0.9. (assume that the scores are normally distributed.) researchers conduct a one-mean hypothesis at the 5% significance level, to test if the mean amount of time parents with young children sleep per night is greater than the mean amount of time last year. the null and alternative hypotheses are h0: μ=6.4 and ha: μ> 6.4, which is a right-tailed test. the test statistic is determined to be t0=1.89 using the partial t-table below, determine the critical value(s). if there is only one critical value, leave the second answer box blank.