Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What was the yield of the K-4 explosion?

### Inputs:
table_name: table, columns: ['Explosion', 'Location', 'Date', 'Yield (approximate)', 'Altitude (km)', 'Nation of Origin']

### Response:
SELECT Yield (approximate) FROM table WHERE Explosion = K-4