You can use a large plastic bottle,______cut off, as a pot to grow young plants in.

B the top of which

D with its top

选D 是with 复合结构：with + 宾语 + 过去分词（宾补）。cut off 是过去分词。瓶子的顶端是被切掉的。完整的句子需使用被动语态：Its top was cut off.

如果选B 的话，是定语从句，从句需要体现被动语态。以下两句任选其一：

You can use a large plastic bottle, the top of which  was cut off, as a pot to grow young plants in. （定语从句）

You can use a large plastic bottle, with its top cut off, as a pot to grow young plants in. （with 复合结构）