Which best describes a mudflow? sudden movement along a flat, inclined surfacemovement too slow to be observed directlymaterial moving downslope as a thick fluidmaterial falling freely through the air

I just took the quiz and can confirm that the right answer is "material moving downslope as a thick fluid".

Source/Explanation (from my textbook) (keywords that I think best match the right answer have been underlined by me):

Flows are mass movements of material containing a large amount of water, which move downslope as a thick fluid. Flows that move quickly, called mudflows, are common in semiarid mountainous regions, such as parts of southern California.

tocharian and anatolian were belaved to become extinct during the ninth century. =)