In the figure above, line AC represents a seesaw that is touching level ground at point A. If B is the midpoint of AC, how far above the ground is point C ？（）
(1)x=30
(2)Point B is 5 feet above the ground.
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．
