Change into passive! George had repaired many cars before he received his mechanic's license.

• A. many cars had been repaired by george before he received his mechanic's license.
• B. before he received his mechanic's license, many cars had been being repaired by george.
• C. before he was received his mechanic's license, many cars had been repaired by george.
• D. many cars had been being repaired by george before he was received his mechanic's license.