Which revision correctly combines these sentences?
My computer was working very slowly. I had to restart it for the updates to take effect.
A My computer was working very slowly, I had to restart it for the updates to take effect.
B My computer was working very slowly and I had to restart it for the updates to take effect.
C My computer was working very slowly I had to restart it for the updates to take effect.
D My computer was working very slowly; I had to restart it for the updates to take effect.