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.

Sentence: 'a man walking a brown horse down a race track'. Reverse all words of length '4' in the given sentence.
a man walking a brown horse nwod a ecar track

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

Sentence: 'a fire hydrant sits in the middle of a flooded street'. Reverse all words of length '7' in the given sentence.

a fire tnardyh sits in the middle of a dedoolf street