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    Many people like traveling during their vacation. They go to mountains, seaside, or forests. Some people like history so they like to visit old castles  (城堡), museums and monuments  (纪念, 碑). In many foreign countries, the travel agent (旅行社) can help you plan your holiday. You can tell the travel agent what kind of holiday you like, how much money you want to spend, and the travel agent will give you a lot of information about where to go, how to get there, where to stay, and what kind of activities you can do there. One of the holidays is called "package holiday". That is, you just pay the money, and the travel agent will plan everything for you, the ticket for the train or plane, the hotel, the activities, etc.

“自隋以来，平民社会，穷困子弟，十年寒窗，也可跃登上第。”材料表明穷困子弟“跃登上第”的主要途径是（    ）

若曲线$y=x^4$的一条切线$l$与直线$x+4y-8=0$垂直，则$l$的方程为（      ）

李伯伯要修23张凳子，已经修好了3张，还要修____张凳子。