Final answer:
Infectious diseases can spread by two different methods when airborne or by touching contaminated objects: airborne transmission for droplet inhalation, and contact transmission for direct or indirect contact.
Step-by-step explanation:
When an infectious disease spreads through the air or makes contact with a contaminated object, it is referred to as either C. Airborne transmission or D. Contact transmission, respectively. Airborne transmission occurs when pathogens in droplets are expelled from an infected host's respiratory system during coughing or sneezing and are then inhaled by nearby individuals. In contrast, contact transmission can occur when there is direct contact between an infected person and a new host, such as through skin-to-skin contact or touching the same surfaces. Common cold and flu viruses are examples of pathogens that can spread by airborne transmission. On the other hand, diseases like athlete's foot and warts can spread through contact transmission.