What command line redirection characters instruct the shell to read from the current input source

What command line redirection characters instruct the shell to read from the current input source until a specific word, on a separate line and without leading and trailing characters, is reached?

A.
<<

B.
<l

C.
!<

D.
$<

Explanation:
Example:
$ echo <<foobar
Hello
foobar
Hello