I found this a the correct answer for one of the Kaplan
SC questions. However, I do not understand why a fabric and have been do not agree in number? Is not fought to has been invented the right answer?
A scientist has determined that a recently discovered ancient Chinese weapon, buried since approximately 1300 B.C., is encrusted with silk, a fabric previously thought to have been invented 1000 years later.
I appreciate your clarification.