Multi-select problem: How does the next paragraph end?

How to cascade routers
Designate which one of your routers will be the primary router and which will be secondary.
Your primary router should already be configured as, or with, your modem.
Connect your computer directly to your secondary router using an ethernet cable by plugging the cable into one of the numbered ethernet ports on the back of the router and to an ethernet port on your computer.

Available choices:
(I) Once the connection is made, the router doesn't need to be connected to the primary router. Connect your router to your modem..
(II) Power on your modem and connect it to your router. Connect your computer to the modem by pressing " connect..
(III) Make sure it is not plugged into your primary router. Access your router's web-based configuration menu..
(IV) Connect the router to the usb port on your modem. The usb port on your modem will serve as a primary router..
(III)