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 bear is standing and looking down at something that is in its hands'. Reverse all words of length '4' in the given sentence.

the raeb is standing and looking nwod at something taht is in its hands