Approximately _____ of the country's adult population has internet access.

a. one-third
b. two-thirds
c. one-quarter
d. three-quarters

I am guessing d. the others seem to low. The book states that the number of U.S. internet users hit 194 million in 2008 (85 percent of families), each averaging 15 hours a week online.

It's asking about the "adult population" -- does that make a difference?

I think you're probably right, but check out a few of these search results first:
http://www.google.com/search?q=us+adult+population+with+internet+access&oq=us+adult+population+with+internet+access&aqs=chrome..69i57j69i64.8340j0j7&sourceid=chrome&es_sm=119&ie=UTF-8

Keep in mind that your study materials may be a little outdated (check the copyright date) and things change very fast. But choose the answer that is closest to what your book says.

This site has interesting numbers and graphs:

http://www.census.gov/popclock/

To calculate the approximate percentage of the country's adult population that has internet access, we can use the information provided in the book. According to the book, the number of U.S. internet users in 2008 was 194 million, which accounted for 85% of families.

To determine the approximate percentage of the adult population, we need to make an assumption about the average family size. Let's assume an average family size of four members (which is a rough estimate).

So, the total number of internet users can be calculated as follows:
Total number of internet users = 194 million * (1 / 0.85) (to account for the 85% of families)

Assuming each family has four members, the total population is:
Total population = Total number of internet users * 4

Now, to calculate the approximate percentage of the country's adult population that has internet access, we divide the total number of internet users by the total population and multiply by 100:

Percentage of adult population with internet access ≈ (Total number of internet users / Total population) * 100

Let's plug in the values to calculate the approximate percentage:

Total number of internet users = 194 million * (1 / 0.85) ≈ 228 million
Total population = Total number of internet users * 4 ≈ 912 million

Percentage of adult population with internet access ≈ (228 million / 912 million) * 100 ≈ 25%

Therefore, the correct answer is c. one-quarter, which corresponds to approximately 25% of the country's adult population having internet access.