题目

 The company _____ a rise in salary for ages, but nothing has happened yet.      A. promised     B. is promising     C. is promised     D. has been promising 答案：D导致现代人人种差异的主要原因是  [     ]A．体貌特征不同B．进化阶段不同C．生活习俗不同D．不同自然地理环境等多种因素的长期影响