In this task, you need to remove 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: 'boats sailing along a river next to a cliff with buildings on it'. Remove all words of length '4' in the given sentence.
boats sailing along a river to a cliff buildings on it

Sentence: 'a bear rolling on his back on some logs'. Remove all words of length '2' in the given sentence.
a bear rolling his back some logs

Sentence: 'a train heading down the train tracks in an open field'. Remove all words of length '6' in the given sentence.

a train heading down the train in an open field