Find the synonym of the highlighted word: The professor tried to stimulate interest in archaeology by taking his students on expeditions. 

• A synonym of a A synonym of a word refers to the meaning of a word that is similar to the meaning of another word. For example, sad and sorrow are synonyms.
• Stimulate refer to increasing interest of someone.
• Option A is incorrect because the professor did not try to oppress the students. Oppressive refers to controlling someone with the help of power. For example, the powerful person oppresses the weak person.
• Option B is an incorrect answer because fake refers to  something which is not true or not real. For example, He buy a fake Gucci cap.
• Option C is the correct answer, encourage refers to increasing interest or increasing enthusiasm.
• Option D is an incorrect answer because ‘diminish’ refers  to decrease in size . For example, the tiger is diminishing day by day because of poaching.
• Synonym of the word 'stimulate' is encourage.

Hence, option C is the correct answer.