Which of the following statement is correct for two wattmeters method of power measurement in 3 phase circuit?

• A. Power can be measured by this method only for star connected loads
• B. When two wattmeters have equal readings power factor is 0.5.
• C. When power factor is 1, one of the wattmeters readings is zero
• D. When the two wattmeter read equal and opposite, p.f. is zero.