• (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．

At a restaurant, Luis left a tip for his waiter equal to 20 percent of his entire dinner check, including tax. What was the amount of the dinner check
(1) The sum of the dinner check and the tip was $16.80.
(2) Luis’ tip consisted of two bills and four coins.