Step 1 :Samples of DNA are collected, and the four DNA bases of A, G, C, and T are coded as 1, 2,3, and 4, respectively. The results are listed as $1,1,2,3,4,3,4,3,3,2$.
Step 2 :The confidence interval for the population mean $\mu$ is calculated as $1.9<\mu<3.3$ (Round to one decimal place as needed).
Step 3 :The practical use of the confidence interval is to estimate that, with 95% confidence, the interval from 1.9 to 3.3 actually contains the true mean DNA base of all people.
Step 4 :This interpretation is correct because a confidence interval is a range of values, derived from a data set, that is likely to contain the value of an unknown population parameter. In this case, the population parameter is the mean DNA base of all people.
Step 5 :Even though the numbers are substitutes for the DNA base names, they still represent a quantitative measure and can be used to calculate a confidence interval.
Step 6 :Final Answer: \boxed{\text{A. The confidence interval can be used to estimate that, with 95% confidence, the interval from 1.9 to 3.3 actually contains the true mean DNA base of all people.}}