Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_23944006_4 (surface VARCHAR, opponents VARCHAR)
### Question:
Name the surface for cara black rennae stubbs
### Answer:
SELECT surface FROM table_23944006_4 WHERE opponents = "Cara Black Rennae Stubbs"