Which is the best example of a strong conclusion in a presentation?

a: studies have shown that bottled water is not any safer than tap water in most communities. the fda requires technicians to test all tap water before it is distributed.

b: another argument against bottled water is the waste that is produced in making and disposing of the plastic bottles. distributing cases of water creates pollution and traffic.

c: drinking tap water instead of bottled water is a simple thing. it is inexpensive, saves the environment, and tastes great. why buy bottles? fill your glass at the tap and enjoy!

d: do you think you can taste the difference between expensive bottled water and the water that comes from your tap? we took a poll of students here in our school. here are the results.