Answer:
D. A higher number of smartphone extended warranty contracts were sold during 2018.
Step-by-step explanation:
2017 2018
Revenue $851 $943
Deferred Revenue (ending balance) $347 $668
Deferred revenue refers to the money a company receives from clients as prepaid services, which creates a liability to the company. The liability is generally reported as unearned revenue and must be accrued as the service is provided.
The only option that can result in an increase of unearned revenue is the sale of extended warranties that last more than a year.