题目

When Johnson called again, the manager received him very politely. “That is a most remarkable oil you brought us, Mr Johnson,” he said. Johnson nodded his smooth, dark head. That was something he knew very well. “I’ve never seen anything like it,” the manager admitted. Johnson nodded again. “No?” he said politely. Then he added, “But I think you will, sir. A very great deal of it.” He appeared to think for a moment. “I think you will find it will be on sale seven, perhaps, eight years from now.” He smiled. The manager thought that was uncertain. He said, “It is better t函数           （    ）     A．图象无对称轴,且在R上不单调          B．图象无对称轴,且在R上单调递增     C．图象有对称轴,且在对称轴右侧不单调            D．图象有对称轴,且在对称轴右侧单调递增