What two devices are responsible for converting the data from the WAN service provider into a form acceptable by the router? (Choose two).

the serial port of the router
a modem
a switch
the ethernet port of the router
a CSU/DSU device
a DTE device

ccna exploration 2 chapter 2 Exam Question And Answers 

What two devices are responsible for converting the data from the WAN service provider into a form acceptable by the router? (Choose two).