Which compound sentence is not correctly punctuated?
AHis new watch is self-winding; it still needs a battery.
BHis new watch is self-winding, but it still needs a battery.
CHis new watch is self-winding but it still needs a battery.
AHis new watch is self-winding; it still needs a battery.
BHis new watch is self-winding, but it still needs a battery.
CHis new watch is self-winding but it still needs a battery.