—Have you ever _______ any activities during the summer vacation?

—Yes, I've helped in a disabled children's home. [ ]

A. caught up with

B. taken part in

C. got used to

D. gone on

某学生为了证明甲烷中含有碳、氢元素，设计并完成了如下实验方案，请你帮他完成下面的实验报告：

实验目的：证明甲烷中含有碳、氢元素

实验用品：火柴、盛有甲烷的贮气瓶、一个洁净干燥的小烧杯、澄清石灰水