Step 1: Know what punctuation marks do:
Punctuation marks are signs that show where to stop, pause or ask a question. They make a written sentence clear.
Step 2: Count the basic marks:
The basic signs are the full stop, comma, question mark, exclamation mark, colon, semicolon, apostrophe, quotation marks, hyphen, dash, parentheses, brackets, braces, ellipsis and slash.
Step 3: Match with the options:
The list above has 15 signs. So 10 and 12 are too few, and 20 is too many.
Final Answer:
There are 15 basic punctuation marks or signs used in English. The correct option is (C).