AJ is absolutely correct.
The green dotted line denotes a radial of a VOR that the crew have put into the radios aids page of the FMC to cross check that the route, which appears to turn to the right, over the VOR, is cross-checked.
An extended centreline of a runway shows up as a white dotted line, but only extends for 14.2NM in the ND scale of 10, 20 or 40 so would not appear right across the whole ND like that.
As for the green arc, AJ
is also correct. The green arc is based on 3 things only. MCP altitude, current rate of climb/descent, and groundspeed. In turbulence, when the aircraft is being bounced around, the green arc comes in, and out and in and out as the aircraft fights to be stable. In these conditions, the green arc is a useless tool. In stable conditions it can be very useful, especially when doing a VOR approach to make sure that you reach a certain DME
at a certain altitude while doing a continuous descent.