If you do not have autodeposit enabled on your bank account that receives your Interac Etransfer withdrawals, you will be required to input an answer to a security question in order to accept your funds.
In these instances, your account ID, which can be found going to the deposit CAD page, or at the top of any transaction confirmation email sent to you, will be the answer to the security question. Entering this ID as the answer will have the funds released to your account.