Definition: 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.
Input: Sentence: 'the man is jumping above the bed behind the woman sitting on it'. Reverse all words of length '7' in the given sentence.

the man is gnipmuj above the bed behind the woman gnittis on it