Which revision correctly combines these two sentences?
I overslept by thirty minutes this morning. The bus left without me.
A. I overslept by thirty minutes this morning so the bus left without me.
B. I overslept by thirty minutes this morning; the bus left without me.
C. I overslept by thirty minutes this morning, the bus left without me.
D. I overslept by thirty minutes this morning the bus left without me.