题目

---Why did John ask me about the problem? ---________, he tried to find a better way to settle it. A. Not to be satisfied          B. Don’t satisfy C. Not being satisfied          D. Not satisfied 答案：D如果m，n是两个不相等的实数，且满足m2-2m=1，n2-2n=1，那么代数式2m2+4n2-4n+1999=________．