Which of the following statements regarding the Malthusian Theory are correct?

1. Malthus believed that positive checks, such as famine and disease, were necessary to control population growth.
2. Malthus assumed that population grows geometrically, while food supply grows arithmetically.
3. Malthusian theory predicted that agricultural advancements would prevent population from exceeding food supply.
4. Preventive checks, such as delayed marriage, were advocated by Malthus to control population growth voluntarily.