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

### Instruction:
What shows for the Longitude when there is a Diameter (km) of 31km?

### Inputs:
table_name: table, columns: ['Gill', 'Latitude', 'Longitude', 'Diameter (km)', 'Diameter (mi)']

### Response:
SELECT Longitude FROM table WHERE Diameter (km) = 31km