When working in contemporary corporate cultures the most important rule is CYA.

CYA = cover your ass

If your manager asks you to do B instead of A - which you think is the correct solution, you write them an email. You write that in your opinion A is correct and that you understand he wants you to do B instead. You ask him to correct you if you are wrong.

If you are ever told you did it wrong you forward the person the email thus proving it wasn't your idea to go for B.

When working in contemporary corporate cultures the most important rule is CYA.

CYA = cover your ass

If your manager asks you to do B instead of A - which you think is the correct solution, you write them an email. You write that in your opinion A is correct and that you understand he wants you to do B instead. You ask him to correct you if you are wrong.

If afterwards you are told you did it wrong and should have gone for A you forward the person the email thus proving it wasn't your idea to go for B.