丁丁要赶红 黑 白 灰不同颜色的马过河,红马过河.红马过河要4分钟,黑马过河要6分钟，白马过河要3分钟，

首先它肯定要过去三趟，回来两趟，才能完成4匹马。
有两种极端方法。
一：使得回来的两次时间最短。
那就是用三分钟的马为桥梁，每一次带一匹马过河，再骑三分钟的马回来。
这样的话，过去的时间为4+6+9=19分。回来的时间为3+3=6分。
总时间 = 19+6=25分。
二：使得过去的三次时间最短。
九分钟的马过河那次肯定要9分钟，那么这次尽量搭配6分钟的马。剩下的两次过河都取最少的三分钟马搭配四分钟马的模式。所以这个流程是：
【3+4】过去→【3】回来→【6+9】过去→【4】回来→【3+4】过去。
这样整个的时间为：4+3+9+4+4=24分。
所以方式二的时间更短，为24分钟。
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myet 六分钟口语测试六十个句子都什么

But at last he knew that he was going to die. He had just strength to fly up to the Prince's shoulder once more. Good-bye, dear Prince! he murmured, will you let me kiss your hand?
I am glad that you are going to Egypt at last, little Swallow, said the Prince, you have stayed too long here; but you must kiss me on the lips,for I love you.
It is not to Egypt that I am going, said the Swallow. I am going to the House of Death. Death is the brother of Sleep, is he not?
And he kissed the Happy Prince on the lips, and fell down dead at hisfeet.
At that moment a curious crack sounded inside the statue, as if something had broken. The fact is that the leaden heart had snapped right in two. It certainly was a dreadfully hard frost.