Most of the oil that pollutes the ocean comes from

Question

a.operating boats and personal watercraft
b.spills from oil tankers
c.runoff from cities and towns
d.leaking underground storage facilities

I picked d. That made sense to me. something that is leaking from facilities will pollute water right?

http://www.trb.org/news/blurb_detail.asp?id=655
Drop by drop—that is how most oil enters the oceans. Catastrophic spills make the headlines, but it is the chronic dribble, dribble, dribble of seemingly small inputs that supplies most of the oil polluting the world’s oceans.- Oceanus magazine

http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/peril_oil_pollution.html

So is it b.?

c

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