Which Liquid water produces more soap foaming?

Question

Using the following Liquid Water samples:

(a) Tap Water;

(b) River water;

(c) Sea water;

(d) Rain water and

(e) bottled water

Putting them in order of more soap foaming to the least soap foaming.

Explain, what makes the soap foaming to be different from each liquid water?

Answer 1

d. The least amount of minerals in the water, the more water surface is available to activate the soap's potential to create bubbles and foaming.  Bottled water would likely be next.  However, the minerals that are natural in ground aquifers (as used by utilities) are useful in the body, particularly for growing children.  d., e., b., a., c.

Answer 2

The softer the water the more foam.  If you dont know what I mean then check wikipedia.  I'm guessing this is homework?