In this task, you need to remove all words of a given length in the sentence. The number of letters in a word determine its length, for example, the length of the word "apple" is 5.

Sentence: 'a black bear sitting on top of a fallen log at a zoo'. Remove all words of length '7' in the given sentence.
a black bear on top of a fallen log at a zoo

Sentence: 'a london bed and furniture store called happy nightmares'. Remove all words of length '3' in the given sentence.
a london furniture store called happy nightmares

Sentence: 'a young man getting ready to serve a tennis ball to his opponent'. Remove all words of length '7' in the given sentence.

a young man ready to serve a tennis ball to his opponent