By creating a permanent water supply
Hope this helped
The answer is their because "the girls" is plural, meaning more than 1 girl is being addressed. Therefore, the answer cannot be her.
The answer is the first one.
In "Writers often disavow the notion of a 'literary duty'" the author conveys a somewhat condescending attitude, as if they would always follow this and set aside anyone who said otherwise. This attitude says the author is looking down on them, and that the author believes that many authors do not meet their standards.
Another answer I would consider is "...writers ruined by their shrill commitments." However, there is no context or clear tone. The author could be mournful of the lost potential for all we know.
If I understand what you’re asking, it should be how much milk do you drink, how many people live in Athens, how many times do you go to the park, how much are these boots, how much money do you spend.