It is important (as you should know) to turn off your cell phone at the doctors office.
Explanation:
Brackets (parentheses) are punctuation marks used within a sentence to include information that is not essential to the main point. Information within parentheses is usually supplementary; were it removed, the meaning of the sentence would remain unchanged. We can easily remove the phrase, <em>"as you should know"</em>, and the sentence would still make sense.
