m is a two digit number (位数) and 2m is a three digit number (三位数)，what is the unit digit (个位) of m
(1)the unit number of 2m is 4
(2)the unit number of m is the same as the tens number (十位数) of 2m
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．