When Specifying Multiple Variable Names and Values for a Playbook

Multiple Choice

When specifying multiple variable names and values for a playbook on the command line, which of the following is the correct syntax?

A) ansible-playbook playbook.yml -e `host="foo" pkg="bar"'
B) ansible-playbook playbook.yml -e `host: "foo", pkg: "bar"'
C) ansible-playbook playbook.yml -e `host="foo"' -e `pkg="bar"'
D) ansible-playbook playbook.yml --extra-vars "host=foo", "pkg=bar"