Answer:
a. Paolo recruited job applicants for the company that showed promise.
The error in this sentence is a: AMBIGUITY.
b. We will be visiting our accounts in California, Oregon, and visiting our accounts in Washington.
The error in this sentence is a: LACK OF PARALLELISM.
You work for a printing company, and you realize that your colleague sent incorrect price quotes to a client. You begin to write an e-mail to the client to apologize for the mistake. You want to remedy the situation without criticizing your colleague.
The sentence is missing, so I looked for a similar question:
"Bill made an error when he was processing your invoice."
The sentence excerpted from the e-mail uses ACTIVE voice. Given the purpose of your message, this voice IS NOT appropriate.