Answer: 4. covering the original text with a material
There are four main types of forgery.
1. blind forgery, the type that is easiest to detect because the forger has no sample of signature to be forged thus forged signature it is not close to a genuine signature
2. simulation, this is where the forger has a sample of the signature to be forged.
3. covering the original text with a material then tracing the signature, and
4. Optical transfer with the use photocopier, scanner or photography.