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 cows on a field of grass with trees in the background'. Reverse all words of length '1' in the given sentence.
Example Output: many cows on a field of grass with trees in the background

Example Input: Sentence: 'a person at a zoo looking over the fence of a giraffe enclosure'. Reverse all words of length '6' in the given sentence.
Example Output: a nosrep at a zoo looking over the fence of a giraffe enclosure

Example Input: Sentence: 'a guy opening his mouth wide for food'. Reverse all words of length '1' in the given sentence.
Example Output:
a guy opening his mouth wide for food