It is required to measure the true open circuit e.m.f. of a battery. The best device is

A. worst, ventilation B. poor ventilation C. better ventilation D. none of the above

A. Tractive B. Portative C. Either of the above D. None of the above

A. Method of average losses B. Equivalent current method C. Equivalent torque method D. Equivalent power method E. All of the above

A. solid B. hollow C. perforated D. any ofthe above