The correct option is A It allows a writer to provide additional information.
Parenthesis are marked by these brackets ( ) which contain a word or phrase, sometimes even a sentence that provides additional information. Without these words, the sentence surrounding it is grammatically correct. For example, 'The reporter Mr. Shekhar (along with his intern) came to the press conference.' Here the information in the brackets merely provides extra information and the sentence is complete if these words 'along with his intern' are omitted. Hence the correct option is A. Braces { } (or curly brackets) are used in certain mathematical expressions and in programming languages. Parenthesis is not used for this purpose, hence option B is incorrect. Option C is a characteristic of angle brackets < > which is used to enclose an email address, like <abcd@yahoo.com> and isn't a function of parenthesis ( ), hence option C is incorrect. Square brackets [ ] are used to provide clarification, for example, 'She [Susan] came to meet me yesterday.' This isn't the function of parenthesis, hence option D is incorrect.