This is level 1 of the I-Tunnel.
This is a tutorial to sideways conveyors. Simply jump right three times at the ring of conveyors, then when you get to the big conveyor at the end, keep jumping left, (but be careful and don't fall off the platform).
Since this is a tutorial level, this is not too hard. You should be able to make quick work out of this level.
New Tunnel Edit
It is not seen until Level I-2, but the C-tunnel is actually unlocked from beating Level I-1. This is like the Low-power Tunnel, in which you can see the New Tunnel in Low-power Tunnel, part 14, but is not unlocked until you beat Low-power Tunnel, part 15.