Regarding request for 2 passports in 1 application

[pchanso]

Hello, I am Indian student residing in the US. Me and my wife (also a student) submitted a combined visitor application to Canada which got approved. Now, I need to send both of our passports to the case processing centre in Ottawa. For that, should I send the passports separately with each having its own return label, or together with just one single return label, or together with a separate return label for each passport.