In this task, you need to reverse 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.

Example Input: Sentence: 'many pairs of open scissors sit on top of metal poles'. Reverse all words of length '4' in the given sentence.
Example Output: ynam pairs of nepo scissors sit on top of metal poles

Example Input: Sentence: 'a group of people sitting on a wooden bench'. Reverse all words of length '1' in the given sentence.
Example Output: a group of people sitting on a wooden bench

Example Input: Sentence: 'a small black elephant standing in the middle of a road'. Reverse all words of length '8' in the given sentence.
Example Output:
a small black tnahpele gnidnats in the middle of a road