Which command displays the output of the foo command on the screen and writes it to /tmp/foodata?

The command that displays the output of the foo command on the screen while simultaneously writing it to the file /tmp/foodata is the one that utilizes the tee command. The tee command takes standard input and writes it to both standard output and one or more files. This means that as the foo command generates output, it will appear on the screen for immediate viewing while also being saved to /tmp/foodata for later reference.

This capability is particularly useful when you want to monitor the output of a command in real-time while also preserving that output for future use. The tee command allows for this dual functionality seamlessly.

In contrast, other options do not achieve this combined effect. Some may only redirect output to a file or send it to a command but do not display it on the screen. The use of tee is essential here for accomplishing both goals.