In what was then the largest environmental enforcement case in US history, companies including industry leaders Caterpillar Inc, Cummins Engine Co, Mack Trucks and Volvo Truck Corp agreed to pay $US83.4 million in fines and reprogram the computers.
Utilize the input text as a context reference, choose the right relationship between 'Volvo' and 'Truck' from the options.
Options: manufacturer, headquarters location, product/material produced, chief executive officer