Read the following article and answer the question by choosing from the options.

This allows the side frame to pivot so the wheels stay in good contact with the rail over any rough track work . Granted they do not move much and should not if the track has been layed correctly . The bad news is this is the side I need to add the extra pick up to . I have read a number of articles where the extra pickups are always added to the bottom of the truck and rub on the backside of the wheels .

What am I working on that I may have to add an extra pick up ?
Available options:
[1]. I am working on the wheels of a large farm tractor .;
[2]. I am working on a truck and may need to install more parts .;
[3]. None of the above choices .;
[4]. I am working on a car that may be used in a race .;...A:
[2].