The verb ${\color{Red}{\text{know}}}$ means to be aware, to be informed, to recognize, to understand, or to be acquainted with. The past form of ${\color{Red}{\text{know}}}$ is ${\color{Blue}{\text{knew}}}$ ; the past participle form is ${\color{Purple}{\text{known}}}$.
${\color{Green}{\text{No}}}$ (which can function as an adjective, an adverb, or an interjection) means the opposite of yes: not so, not in any degree. ${\color{Green}{\text{No}}}$ can also be used as an exclamation to give force to a negative statement.
You should ${\color{Red}{\text{know}}}$ when to say ${\color{Green}{\text{no}.}}$
Correct Answer $:\text{D}$
Reference: https://www.wikihow.com/Understand-the-Difference-Between-Know-and-No