Which water type is densest?
a. warm, saline water
b. cold, saline water
c. warm, non-saline water
d. cold, non-saline water

Liquid water (freshwater) at about 39 degrees F (4 degrees C) is densest in the ambient environment.

One could argue that water at the deepest parts of the ocean is most dense - due to immense hydrostatic pressures, but that is another matter.
;) have a great day