题目

—Mum, I’m tired of doing too much homework every day. —Oh, dear, without hard work, you can’t _______ your dream. A. choose                  B. encourage           C. manage                D. achieve 答案： D    已知数列与数列的前项和分别为，且满足，，,则当取最大值时，的值为 A．B．C．D．或