Explanation:

- The sentence is in the present tense, referring to a future action.

- Option 1: "it rains" – This option is correct. The sentence suggests you will play unless there's rain.

- Option 2: "it doesn’t rain" – This would mean you will play only if it rains, which contradicts the typical use of "unless."

- Option 3: "it rained" – This is past tense and doesn't fit a future context.

- Option 4: "it may rain" – This suggests uncertainty, which doesn’t fit the structure with "unless."