Answer:
He should add words that are similar to the unknown word.
Explanation:
The inclusion of explanation clues in a sentence is with the intention of giving a more and understandable explanations for any unknown word used. This allows the readers to understand the words that the writer used.
So, for a writer to provide explanation clues, he/she must add words that are similar to the unknown word. This is because similar words will help enable the reader to understand the word(s) used and also help them understand the whole sentence clearer. Therefore, Lucas should add words similar to the unknown words.
Thus, the correct answer is the first option.
