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Read the witch's instructions for her apprentice and select the best word to complete each warning about the levitating cake.
The cake will rise beautifully _________________________ you stir the batter exactly seven times counter-clockwise. Be careful, though! The mixture will explode into a cloud of purple smoke _________________________ you add the crushed dragon scales too early. Keep the oven door firmly shut _________________________ you want the cake to escape and fly around the kitchen!
The cake will rise beautifully provided that you stir the batter exactly seven times counter-clockwise. Be careful, though! The mixture will explode into a cloud of purple smoke if you add the crushed dragon scales too early. Keep the oven door firmly shut unless you want the cake to escape and fly around the kitchen!
Provided that emphasizes a strict condition (the cake rises only if you stir it exactly seven times).
If introduces the direct cause of the explosion (adding scales too early).
Unless means "except if." You should keep the door shut except if your goal is to let the cake fly away!