对于方程：3x+2y=4，下列说法正确的是（　　）

今年3月至6月初，长江中下游地区降水持续偏少，为近60年来历史同期最少，致使上述地区出现严重旱灾。导致该地区严重灾情的主要原因是（　　）

已知函数$f\left(x\right)=\sin \left(2x+\frac{\pi }{3}\right)$，若存在$a\in \left(0,\pi \right)$，使得$f\left(x+2a\right)=f\left(x\right)$恒成立，则a的值是（   ）

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                                                                                                        信仰之光
      ①信仰，就是相信人生中有一种东西，它比自己的生命重要得多，甚至是人生中最重要的东西，值得为之活着，必要时也值得为之献身。这种东西必定是高于我们的日常生活的，像日月星辰一样在我们头顶照耀，我们相信它并且仰望它，所以称作信仰。但是，它又不像日月星辰那样可以用眼睛看见，而只是我们心中的一种观念，所以又称作信念。
      ②真正的信仰是相信人生应该有崇高的追求，真正看重信仰的人决不盲目相信某一种流行的宗教或别的什么思想，而是通过独立思考来寻求和确立自己的信仰。两千四百年前，苏格拉底的信仰就是：人生的价值在于爱智慧，用理性省察生活尤其是道德生活。他为自己的信仰献出了宝贵的生命。
      ③信仰是内心的光，它照亮了一个人的人生之路。没有信仰的人犹如在黑暗中行路，不辨方向，没有目标，随波逐流，活一辈子也只是浑浑噩噩。当然，一个人要真正确立起自己的信仰，这不是一件容易的事。在我看来，在信仰的问题上，真正重要的是要有真诚的态度。所谓真诚，第一就是要认真，既不是无所谓，可有可无，也不是随大流，盲目相信；第二就是要诚实，决不自欺欺人。有了这种真诚的态度，即使你没有找到一种明确的思想形态作为你的信仰，你也可以算作一个有信仰的人了，因为你至少是在信仰着一种有真诚追求的人生境界。

    Increasingly, over the past ten years, people-especially young people have become aware of the need to change their eating habits, because much of the food they eat, particularly processed food, is not good for the health. Consequently, there has been a growing interest in natural foods: foods which do not contain chemical additives and which have not been affected by chemical fertilizers（化肥）widely used in farming today.

    Natural foods, for example, are vegetables, fruit and grain which have been grown in soil that is rich in organic matter. In simple terms, this means that the soil has been nourished by unused vegetable matter, which provides it with essential vitamins and minerals. This in itself is a natural process compared with the use of chemicals and fertilizers, the main purpose of which is to increase the amount but not the quality of foods grown in commercial farming areas.

    Natural foods also include animals which have been allowed to feed and move freely in healthy pastures（生活状况）. Compare this with what happens in the mass production of poultry（家禽）: there are battery farms, for example, where thousands of chickens live crowded together in one building and are fed on food which is little than rubbish. Chickens kept in this way are not only tasteless as food; they also produce eggs which lack important vitamins.

    There are other aspects of healthy eating which are now receiving increasing attention from experts in diet. Take, for example, the question of sugar. This is actually a nonessential food! It is not that sugar is harmful in itself. But it does seem to be additive: the quantity we use has grown steadily and in Britain today each person consumes an average of 200 pounds a year! Yet all it does is provide us with energy, in the form of calories. There are no vitamins in it, no minerals and no fibre.