根据句意和汉语注释，写出单词的正确形式。
(1)The ____  （建议）they have offered us are very useful, we should take them.
(2)Beijing is the capital of China, it is also the ____ （文化）center of China.
(3)Tonight, they are going to celebrate their father's ____  (四十) birthday.
(4)How beautiful those circles on those ____  (蝴蝶)wings are!

将曲线c按伸缩变换公式$\left\{\begin{array}{c}x\text{'}=2x\\ y\text{'}=3y\end{array}\right.$变换得到曲线方程为x^/2+y^/2=1，则曲线c的方程为（　　）

下列观点中与可持续发展要求相符合的有（　　　）
①“围湖造田，毁林开荒”     ②“经济要上，人口要降”　
③先污染，后治理　               ④“但留方寸土，传与子孙耕”