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 blonde lady answered her cell phone because she was waiting for an important call'. Reverse all words of length '7' in the given sentence.

the blonde lady answered her cell phone esuaceb she was gnitiaw for an important call