Even after experts perform a thorough restoration, paintings and tapestries will still show some evidence of the damage suffering when it was burned.

A
suffering when it was burned

B
suffering as they were burned

C
that each suffered when burned

D
that it had suffered as burned

E
suffered when they were burned

This is a simple question. However, the answer provided was not convincing. Can anyone give good explanations?
[/spoiler]E