一字组多词。

邻____ ____    居____ ____

触____ ____   胆____ ____

    It was Sunday yesterday. The weather was fine. It was sunny and there were no clouds in the sky. Sandy and Sue got up early in the morning. Now they were in the park. It is a big park and it's so beautiful. They saw many people there. Some boys played football on the grass. Some girls danced under the tree. An old man walked beside the lake. A young woman and her little son looked at the fish in the lake. How happy they are!

“我们对雾霾的形成机理和成分确实还没有完全搞透，需要更加深入地研究。”“无论是研究大气的，还是研究土壤的，各相关学科力量都组织起来，进行跨学科集中攻关，真正打一场‘蓝天保卫战’，让大家都看到更多蓝天！”***的观点主要说明（    ）

①认识具有反复性、无限性，促进实践发展

②研究雾霾的根本目的是揭示雾霾产生变化的客观规律性

③雾霾的成因并不单一，研究雾霾要全面把握事物的联系

④研究雾霾成因的目的是治理雾霾

已知函数 $f(x)=|x-a|$ ，不等式 $f(x)\le 3$ 的解集为-1，5