单选题 Last year Luis invested x dollars for one year, half at 8 percent simple annual interest and the other half at 12 percent simple annual interest. Now he wants to reinvest the x dollars for one year in the same two types of investments, but the lower rate has decreased, If the higher rate is unchanged, what fraction of the x dollars must be reinvest at the 12 percent rate s that the total interest earned from the x dollars will be the same for both years?
(1)The lower rate is now 6 percent.
(2)The total amount of interest earned from the two investments last year was $3,000.
(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．