Which statement regarding TFTP is not true?

Which statement regarding TFTP is not true?

A.
Communication is initiated over UDP port 69.

B.
Files are transferred using a secondary data channel.

C.
Data is transferred using fixed-size blocks.

D.
TFTP authentication information is sent in clear text.

E.
TFTP is often utilized by operating system boot loader procedures.

F.
The TFTP protocol is implemented by a wide variety of operating systems and
network devices.