In which ways do sinkholes form? Please select all that apply.

a) A roof of an already formed cavern collapses under its own weight.

b) Lakes with mildly acidic water dissolve the limestone beneath them, leaving
behind sinkholes.

c) Limestone is dissolved by rainwater, the bedrock surface lowers, and
groundwater that is flowing in the passages below washes away the soil.

d) A stream with mildly acidic water continually cuts down into the limestone
until it exposes an underground cavern.

e) Limestone is dissolved by rainwater, and the bedrock surface lowers.