如果对于某一特定范围内的任意允许值，p=|1-2x|+|1-3x|+…+|1-9x|+|1-10x|的值恒为一常数，则此值为（ ）
A．2
B．3
C．4
D．5
∵P为定值，
∴P的表达式化简后x的系数为0；
由于2+3+4+5+6+7=8+9+10；
∴x的取值范围是：1-7x≥0且1-8x≤0，即
≤x≤1 8
；1 7
所以P=（1-2x）+（1-3x）+…+（1-7x）-（1-8x）-（1-9x）-（1-10x）=6-3=3．
故选B．
| 短文改错。 文中共有10处语言错误， 要求你在错误的地方增加、删除或修改某个单词。 增加：在缺词处加一个漏字符号（∧），在其下面写上该加的词。 删除：把多余的词用斜线（\）划掉。 修改：在错的词下划一横线，并在该词下面写上修改后的词。 注意：1. 每处错误及其修改均仅限一词。 2.只允许修改10处，多者（从11处起）不记分。 | |
| Last week we went mountain-climbing. Even the heavy rain in the morning couldn’t prevent us go. Setting off very early, we went along an extreme narrow road. On every side of the road were green fields and some farm house. We could hear the sound of the rain and our footsteps mixing with our laughter. At noon we reached the top of the mountain. That surprised us most was the beautiful scenery. After having short rest there and sharing with the food we had brought, we started going down. It had rained even harder. We were all wet, and we still sang and laughed happily. _____________________________________________________________________________ |