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

### Instruction:
Which Surface has a Round of 4th round, and a Player of maria sharapova?

### Inputs:
table_name: table, columns: ['Player', 'Ranking', 'Event', 'Surface', 'Round', 'Score']

### Response:
SELECT Surface FROM table WHERE Round = 4th round AND Player = maria sharapova