• (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．

Circle O is inscribed in parallelogram ABCD, whose base is 12 inches. Find the area of the shaded portion.
(1) The radius of the circle is 4 inches.
(2) DC is twice as long as AD.

简述土地估价的概念。