Engine 2014: Electricity

1. A machine "A" and machine "B" are both droop machines
2. B machine "A" and machine "B" are both isochronous machines
3. C machine "A" is a droop machine, while machine "B" is an isochronous machine
4. D machine "A" is an isochronous machine, while machine "B" is a droop machine

Tip: press A-D to answer