一个关于英语词组的选择题.

一个关于英语词组的选择题.
He was standing too close to me and I almost____him when I turned around
A knocked down
B knocked into
C knocked over
D knocked against
请帮忙解释句意和每个选项的意思
再帮忙说出为什么选那个答案.
我查了字典，a和c都有撞的意思，但是b我没有发现字典里有这个词，但是我觉得异常困惑
我查的是牛津字典。