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

### Instruction:
Name the birth of the person that has a spouse of frederick iv and became consort of 4 april 1721

### Inputs:
table_name: table, columns: ['Birth', 'Marriage', 'Became Consort', 'Ceased to be Consort', 'Death', 'Spouse']

### Response:
SELECT Birth FROM table WHERE Spouse = frederick iv AND Became Consort = 4 april 1721