Question

Most people in cities get their water _______.
a.
by supplying it themselves
b.
by delivery through pipes
c.
through private suppliers
d.
all of the above

(It's not D)

Answer 1

It would be b, because it's a cheap, and very easy way. 

(because of gravity and pressure and stuff like that)

Answer 2

Most people in cities get their water B. by delivery through pipes.
This is the easiest and the cheapest way to get your water which you can use for showering, bathing, cooking, washing, etc. Not many people choose private suppliers or supplying the water themselves because it is expensive and time-consuming.