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 black cow stands alone in a grassy field'. Reverse all words of length '3' in the given sentence.
Example Output: a black woc stands alone in a grassy field

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: 'someone is holding a computer on top of two plastic barrels'. Reverse all words of length '1' in the given sentence.
Example Output:
someone is holding a computer on top of two plastic barrels