Word Meaning:
- Quack: A person who dishonestly claims to have special knowledge or skill in some field, typically medicine.
- Clown: A comic entertainer, especially one in a circus, wearing a traditional costume and exaggerated makeup.
- Dressmaker: A person who makes women's clothes as a profession.
- Philanthropist: A person who seeks to promote the welfare of others, typically through donations of money, property, or work.
- Charlatan: A person falsely claiming to have a special knowledge or skill; a fraud.

Synonym:
A synonym is a word that has the same or similar meaning as another word.

Matching the Synonym:
Out of the given options, the correct synonym for the word "quack" is "charlatan".

Explanation of Options:
- Clown: A clown is not a synonym for "quack" because it refers to a comic entertainer, wearing traditional costume and exaggerated makeup.
- Dressmaker: A dressmaker is not a synonym for "quack" because it refers to a person who makes women's clothes as a profession.
- Philanthropist: A philanthropist is not a synonym for "quack" because it refers to a person who seeks to promote the welfare of others, typically through donations of money, property, or work.
- Charlatan: A charlatan is a person who falsely claims to have a special knowledge or skill; a fraud. This term is the correct synonym for "quack" as it also refers to a person who dishonestly claims to have special knowledge or skill in some field, typically medicine.

Therefore, the correct option to mark the synonym of the word "quack" is option 'D' - Charlatan.