How can the existing environment variable FOOBAR be sup…

How can the existing environment variable FOOBAR be suppressed for the execution of the script./myscript
only?

A.
unset -v FOOBAR;./myscript

B.
set -a FOOBAR=””;./myscript

C.
env -u FOOBAR./myscript

D.
env -i FOOBAR./myscript