The Technician told us how to maintain the machines in good working order.

A. The technician said to us, “There is how you maintained the machine in good working order.”
B. The technician said “This is how you maintain the machine in good working order.”
C. The technician said to us, “That is how you maintained the machine in good working order.”
D. The technician said to us, “This is how you maintained the machine in good working order.”