instruction:
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.
question:
Sentence: 'a group of people wearing skis and standing at the top of a ski slope'. Reverse all words of length '7' in the given sentence.
answer:
a group of people gniraew skis and standing at the top of a ski slope


question:
Sentence: 'a group of five people in white snow outfits cross country skiing'. Reverse all words of length '5' in the given sentence.
answer:
a puorg of five people in etihw snow outfits ssorc country skiing


question:
Sentence: 'a red and yellow train traveling down tracks next to a platform'. Reverse all words of length '9' in the given sentence.
answer:

a red and yellow train gnilevart down tracks next to a platform