Which of the following is a clue that something has been erased on a document?

The fibers of the paper are disturbed when looked at under a microscope

I suppose this should have choices. Usually, a black felt pen would be used to cover some words and sentences. If an erasure has been used, a white ink has been used to cover some words. If a rubber erasure has been used, one will find bits of rubber around the paper and on the floor of the place where the paper was stored

Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group. This R group, or side chain, gives each amino acid proteins specific characteristics, including size, polarity, and pH.

Chemicals of this type: Alanine