听力原文：M1: Mr. Chen called to see if his car is ready for pick up. Did you finish putting in the new carburetor, Jeff？
M2: No. because I was busy working on the van this morning. You told me last night to have that ready for pick up by noon today, remember？
M1: All right, could you work on Mr. Chen's car right away？ He said he will be coming to pick it up at 4 o'clock, so that should give you plenty of time to do the work. Also, could you ask Mike to change the oil on the pickup truck？
M2: Mike's not here right now. He had to drive Tom to the hospital.
Who are they？

Auto mechanics.
B. Car salespeople.
C. Truck drivers.
Doctors.