课外文言文阅读，完成后面题。

    甘茂①曰：“昔者曾子处费费人有与曾子同名族者而杀人人告曾子母曰曾参杀人曾子之母曰吾子不杀人织自若。有顷焉，人又曰：‘曾参杀人。'其母尚织自若也。顷之，一人又告之曰：‘曾参杀人。'其母惧，投杼逾墙而走。夫以曾参之贤，与母之信也，而三人疑之，则慈母不能信也。（选自《战国策·秦策二》）

注释：①甘茂：战国时期秦武王时的左丞相。②曾子：曾参，字子舆，春秋末年鲁国人，孔子的学生。

下列对文中划线部分的断句，正确的一项是（    ）

下面是关于函数f（x）=|x﹣{x}|的四个命题：①函数y=f（x）的定义域是R，值域是 $0,\frac{1}{2}$ ；②函数y=f（x）的图象关于直线 $x=\frac{k}{2}\left(k\in Z\right)$ 对称；③函数y=f（x）是周期函数，最小正周期是1；其中正确的命题序号是____．

阅读理解

    This happened about one thousand and seven hundred years ago．One day somebody sent Cao Cao, the king of Wei an elephant．Cao Cao wanted to know its weight(重量)．“Who can think of a way to weigh it?”he asked．But nobody knew what to do because there was nothing big enough to weigh it．

    Then Cao Chong, one of the king's young sons, came up and said, “Father, I've got an idea．Let me have a big boat and a lot of heavy stones, and l'll be able to find out the weight of the elephant．''

    Cao Cao was surprised, but he told his men to do as the boy asked．When the boat was ready, the boy told a man to lead the elephant down into it．The elephant was very heavy, and the water came up very high along the boat's side．Cao Chong made a mark along the water line．

    After that the man drove the elephant onto the bank．Cao Chong then told the men to put heavy stones into the boat until the water again came up to the line．

    Cao Chong then told the men to take the stones off the boat and weigh them one by one．He wrote down the weight of each stone and then added up all the weights．In this way he got the weight of the elephant．