Put the verb in brackets into the correct tense. Choose the correct option.
A: If I __________ \(know\) about the park clean up, I ____________ \(sign/up\) to help.
B: Don't worry. There's going to be another one next week.

• has known/would have signed up
• had known/would have signed up
• knew/would sign up
• knew/would have signed up