The Slopes of Most Cinder Cones Are Usually About 30

The slopes of most cinder cones are usually about 30 degrees because _______ .

A) cinder cones are mostly basalt and basalt is too weak to maintain a slope greater than 30 degrees
B) the loose materials ejected from the cone form slopes at that angle of repose
C) they are composites of loose material and lava and the viscosity of the lava requires the slopes to form at about 30 degrees
D) The statement is false; most cinder cones have slopes less than 10 degrees because of the low viscosity of basalt lava flows.