Which of the following contains a vague pronoun reference?

 - They have discovered that sleep has more than just restorative functions. For example, it plays a significant role in strengthening and solidifying memories.
 - Neuroscientists have discovered that sleep has more than just restorative functions. For example, it plays a significant role in strengthening and solidifying memories.
The second answer choice contains a vague pronoun reference. The pronoun they is used without its antecedent.
The first answer choice shows a possible correction for the vague pronoun reference. They has been replaced with neuroscientists.
Neuroscientists have discovered that sleep has more than just restorative functions. For example, it plays a significant role in strengthening and solidifying memories.