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 small bird sitting on the rim of a fountain'. Reverse all words of length '7' in the given sentence.
Example Output: a small bird gnittis on the rim of a fountain

Example Input: Sentence: 'a small elephant standing next to a forest full of trees'. Reverse all words of length '5' in the given sentence.
Example Output: a llams elephant standing next to a forest full of seert

Example Input: Sentence: 'cars are sitting at a traffic light at a busy intersection'. Reverse all words of length '5' in the given sentence.
Example Output:
cars are sitting at a traffic thgil at a busy intersection