根据所学知识完成题目：
— How much are the two pairs of trousers?— They are not expensive. I think one hundred dollars ______ enough.
某地大量捕捉青蛙作为美食，从而导致稻田里害虫大量繁殖，水稻减产，这结果可以说明动物在生物圈中的重要作用是（ ）
