Which of the following contains a vague pronoun reference?

 - For many sitcoms, sound engineers use a laugh track to simulate the laughter of a live studio audience.
 - For many sitcoms, they use a laugh track to simulate the laughter of a live studio audience.
The first answer choice contains a vague pronoun reference. The pronoun they is used without its antecedent.
The second answer choice shows a possible correction for the vague pronoun reference. They has been replaced with sound engineers.
For many sitcoms, sound engineers use a laugh track to simulate the laughter of a live studio audience.