Complete the sentence: ______ you are ready, you can start.

Complete the sentence: ______ you are ready, you can start.

• A. Once
• B. If
• C. Unless
• D. When

Answer: (D)

Timing is the idea here: the sentence needs a word that marks the moment at which starting is allowed. When you are ready, you can start uses when to set the exact future moment that will trigger the action. If you used if, it would suggest a condition that may or may not happen rather than a definite moment; unless changes the meaning to a negation about starting; once could work in some contexts but when sounds more natural and direct for giving permission tied to a specific moment.

Timing is the idea here: the sentence needs a word that marks the moment at which starting is allowed. When you are ready, you can start uses when to set the exact future moment that will trigger the action. If you used if, it would suggest a condition that may or may not happen rather than a definite moment; unless changes the meaning to a negation about starting; once could work in some contexts but when sounds more natural and direct for giving permission tied to a specific moment.