A Big Bulge Sometimes Slowly Grows on the Flank of an Active

Multiple Choice

A big bulge sometimes slowly grows on the flank of an active Cascades volcano.Why?

A) Thick lava flows pile up around the vent.
B) A huge gas bubble released from the magma inflates it.
C) The magma reacts with snow on the volcano, causing magma inflation.
D) The hot magma melts older ash, causing it to expand.
E) Rising magma is pushing it up.