Need some help on using cat command

I have a file "sample.txt" with the content as below:
Hi
This is a Sample Text.

I need a single command using cat which serve the following purpose.

1.display the contents of sample.txt
2.append some text to it
3. and then exit

But, all should be served by a sinle command.

1) Read again this you agreed with:

2) Repost this time correctly filling in: