Answer:
B. 03/10/2018
Step-by-step explanation:
The date placed in service is 03/10/2018 since this was the date that this trailer or machine was delivered for use according to the question.
The date in service can be defined to be the date that an inventory item such as this machine was made available for service or in other words made available for use. We use this date to calculate the depreciation on the serial inventory.