题目

小船过河时，船头偏向下游与水流方向成α角，船相对静水的速度为v，现水流速度稍有增大，为保持航线不变，且在同样的时间到达对岸，下列措施可行的是（） A . 增大α角，增大船速v B . 增大α角，减小船速v C . 减小α角，增大船速v D . 减小α角，保持船速v不变 答案：B-- Has your elder brother returned from Africa yet?-- Yes, but he _________ here for only three days before his company sent him to Australia. A．wasB．has beenC．will beD．would be