The three-lamp synchronisation method is used to synchronise an alternator with an infinite bus. In which of the following conditions will all the three lamps darken and brighten in step?

• A. Phase is not the same, but voltage, frequency and phase sequence are the same.
• B. Frequencies are not the same, but voltages and phase sequences are the same.
• C. Phase sequences are not the same, but voltages and frequencies are the same.
• D. Voltages are not the same, but frequency and phase sequence are the same.