Final answer:
The correct conclusion is that there is not sufficient evidence to conclude that the percentage of teenage mothers has remained the same.
Step-by-step explanation:
The correct conclusion is a. There is not sufficient evidence to conclude that the percentage of teenage mothers has remained the same.
In hypothesis testing, when the null hypothesis is not rejected, it means there is not enough evidence to support the alternate hypothesis. In this case, the sociologist's belief that the percentage of teenage mothers has decreased is not supported by the data. Therefore, the correct conclusion is that there is not sufficient evidence to conclude that the percentage of teenage mothers has remained the same.