Fill in the Blanks: Know vs. No

The sentence requires understanding the correct usage of homophones 'know' and 'no'.

Step 1: Analyze the First Blank

The first blank relates to understanding or possessing information about *when* something should occur. The word that signifies understanding or awareness is 'know'.

Step 2: Analyze the Second Blank

The second blank follows the verb 'say' and represents the specific response or word being uttered. In this context, 'say no' means to refuse or decline. The word used for negation or refusal is 'no'.

Step 3: Construct the Sentence

Combining the words from Step 1 and Step 2, the complete sentence becomes: "You should know when to say no."

Step 4: Select the Correct Option

This sentence structure matches Option 4, which provides 'know' for the first blank and 'no' for the second blank.

Therefore, the correct completion is: You should know when to say no.