Why Do Cinder Cone Volcanoes Have Steep Slopes

Why do cinder cone volcanoes have steep slopes?

A) They are made from lava flows that pile up steeply.
B) They are found near other volcanoes which crowds their ability to spread out.
C) They are made mostly from water and ash that hardens into steep cones.
D) They are made from pyroclastic materials that pile up near where they were erupted.
E) They are made from very thick magma that doesn't flow outward very much.