读相关材料，回答下列问题。

材料一　博斯腾湖是我国最大的内陆淡水湖，该地年降水量不足30毫米，蒸发量却2000毫米以上。湖面万千飞鸟，湖中鱼群游弋，其西北面是面积广阔的芦苇地。出售芦苇成为当地百姓重要的经济来源之一，但总收入并不高。

材料二　博斯腾湖是淡水湖，但是南侧不远有一个槽状盐沼池，池壁和底部均分布有厚厚的盐层。下图为盐池附近的地质剖面示意图。

根据短文，判断正误。

   My name is Mary. I am eleven. Ted is my brother. He is thirteen. We are in the same school. My mother is a teacher. She is a teacher in our school. My father is a teacher, too. He is a Chinese teacher in a college. I have a cat. Its name is Miaomiao. It is white. It is a nice cat. We are good friends.

当m>0，n>0时，若m、n都扩大为原来的k倍，则分式 $\frac{2m+3n}{3m^2+5n^2}$ 的值(     )