夏天，一些植物的叶片上会有白飞虱，很多人会用肥皂水来杀白飞虱，那么肥皂水能杀死白飞虱吗？
I have created five buttons in the view controller. If i clicked the button it goes to the corresponding view. Now i want to display the button in highlighted state when it is clicked. It should go ba
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