To complete the sentence "You cannot succeed unless", we need to choose the correct phrase from the options provided. The use of "unless" implies a condition that must be met for success. In English, "unless" is a conditional conjunction that sets a prerequisite or necessary condition. The correct structure usually requires the clause following "unless" to state what must actually occur for the main clause to be true. Therefore, this implies the positive need for the action mentioned.
Among the given options:
- "you do not work hard." - Incorrect; negates working hard, contradicting the condition needed for success.
- "you shall not work hard." - Incorrect; future tense with negation, not appropriate for setting a condition.
- "you will work hard." - Incorrect; use of future will does not appropriately follow "unless" as it does not set a condition but rather indicates future action.
- "you work hard." - Correct; establishes the necessary condition of working hard for succeeding.
Hence, the sentence is correctly completed as: "You cannot succeed unless you work hard."