In a refinery, the capacity of oil tank A is 70 per cent of the capacity of oil tank B.
How many more gallons of oil are in tank A than in tank B ？（）
(1)Tank A is 90 percent full; tank B is 50 percent full.
(2)When full, tank A contains 50,000 gallons of oil.
A．条件(1)充分，但条件(2)不充分．
B．条件(2)充分，但条件(1)不充分．
C．条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
D．条件(1)充分，条件(2)也充分．
E．条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
