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 gray teddy bear sitting behind an alarm clock'. Remove all words of length '6' in the given sentence.
a gray teddy bear sitting an alarm clock

Sentence: 'a group of zebra standing on top of a lush green field'. Remove all words of length '3' in the given sentence.
a group of zebra standing on of a lush green field

Sentence: 'three giraffes standing right next to each other near some trees'. Remove all words of length '5' in the given sentence.

giraffes standing next to each near some