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: 'a person parasails in water with mountains in the background'. Reverse all words of length '4' in the given sentence.
Example Output: a person parasails in water htiw mountains in the background

Example Input: Sentence: 'a young man is sitting on the side of a bus eating a hot dog'. Reverse all words of length '3' in the given sentence.
Example Output: a young nam is sitting on eht side of a sub eating a toh god

Example Input: Sentence: 'group of antelopes and deer standing outside in a savannah'. Reverse all words of length '9' in the given sentence.
Example Output:
group of sepoletna and deer standing outside in a savannah