如图所示，一个“Y”字形弹弓顶部跨度为L，两根相同的橡皮条均匀且弹性良好，其自由长度均为L，在两橡皮条的末端用一块软牛皮（长度不计）做成裹片可将弹丸发射出去．若橡皮条劲度系数为k，发射弹丸时，每根橡皮条的最大长度为2L（弹性限度内），则弹丸被发射瞬间所受的最大弹力为（设橡皮条的弹力满足胡克定律）（   ）

细菌和真菌的培养通常包括以下步骤，请选择正确的排列顺序（    ）

①配制培养基    ②在适宜的温度下培养    ③接种    ④高温灭菌．

根据短文内容和所给中文提示，在空白处写出单词的正确形式。每空限填一词。

Dear Future Me,

You are leaving school and stepping into a new world. Well done for completing all ____  (那些) difficult lessons!

You've just found out that you've ____  (通过) all your exams and done your best. You know you'll be able to____  (进入) the fantastic high school. At this moment you must be____ (骄傲的) of yourself.

I'm writing this letter to remind you ____ (再一次) about all the things you wanted to do when you were in the____ (第七) grade. I want you to make sure that before you leave school you'll realise your____ (梦想) as Footballer of the School. Remember that you wanted to be a famous ____ (歌手)? Well, I hope you'll win the top role in the school talent show this year.

If you've done ____  (每件事) you wanted to do, you'll now be a popular and____  (聪明的) student, with a successful future ahead of you.

Don't let me down!

I eat too much sweet food. So I have a ____ (tooth).

漳州市著名的水果之乡，当地的水果有（    ）

①苹果  ②龙眼   ③荔枝    ④哈密瓜