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

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

A.
set -a FOOBAR=””;./myscript

B.
env -u FOOBAR./myscript

C.
unset -v FOOBAR;./myscript

D.
env -i FOOBAR./myscript