填 B happening
因为
there is always something happening
是
something is always happening there
的倒装形式.
其他类似例子：
there are people walking
here is a man running
上面 unexected 拼错了,应该是 expected（预料不到的）.
希望帮到了你.
我是加拿大人,前海外英语老师.