Is mixing active and passive constructions in the same sentence grammatically incorrect?<br/><br/>Many cars <b>had been repaired</b> by George before <b>he received</b> his mechanic's license.<br/><br/>passive/active<br/><br/>George <b>had repaired</b> many cars before <b>he received</b> his mechanic's license.<br/><br/>active/active<br/><br/>Many cars <b>had been repaired</b> by George before <b>he was given</b> his mechanic's license.<br/><br/>passive/passive<br/><br/>Thanks.