Now you are in a dinosaur ____park. Coming here, you will find a kind of old ____, dinosaur, which died out millions of years ago. In our park, we are happy to show you ____ dinosaurs, which lived in the Jurassic. The four-storied-building-high grass-eating dinosaurs are submissive (温顺的) and kind. You can ____ towards them and touch them. But the ____  of them are dangerous. The four-legged meat-eating dinosaurs are very cruel. Please don't ____ them and don't try to give them food. The ____ here is very thick and full of all kinds of animals that lived in the Jurassic. Without any special____and the leading of the guide, please don't step into it. OK, I'm sure that our park will ____anyone who comes here and you will ____a lot from it.

实验桌上有下列9种器材：“探究小车速度随时间变化规律”的实验中，下列哪些器材是多余的：____（填编号）．

①打点计时器；   ②天平；               ③低压交流电源；

④低压直流电源；⑤细绳和纸带；         ⑥钩码和小车；

⑦秒表；      ⑧一端有滑轮的长木板；   ⑨刻度尺．