Topic: Synonyms, Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The word "remarkable" refers to something worthy of attention or extraordinary, which often implies that it stands out in a positive way. Among the options provided, "well known" (option C) is the most fitting synonym because it conveys the idea that something is recognized and acknowledged by many people, often due to its excellence or unique qualities.

Option A, "thankful," relates to expressing gratitude and does not share a contextual connection with "remarkable." Option B, "cleenful," seems to be a misspelling or non-standard word and lacks relevance. Option D, "attention," refers to the act of noticing or focusing on something but does not directly describe something that is extraordinary or noteworthy itself.

In contrast, when something is described as "well known," it often suggests that it has gained recognition for its distinctive attributes—whether due to achievement, popularity, or excellence—aligning closely with the meaning of "remarkable." Therefore, C is the correct choice, as it captures the essence of being noteworthy and deserving of attention.