Does It Have to Be Raining for a River to Flood

Does it have to be raining for a river to flood?

A) Yes. Only the rain that falls into the river fills it up and causes it to overflow.
B) Yes. Rain runs off over the ground and into the river causing flooding.
C) No. Snow and rain that fall into the river fill it up and cause it to overflow.
D) No. Rivers can flood after rain has stopped and tributaries have flowed into bigger streams.
E) No. Rivers can flood during droughts without any rain.