Condensation is the process in which a vapor or gas transforms into a liquid state upon cooling. The behavior of condensate on a cooled surface can vary, leading to different modes of condensation. These modes are classified based on the behavior of the condensate and the characteristics of the condensation process.

The correct answer to this question is option 'B', which states that there are two distinct modes of condensation. Let's explore these modes in detail:

1. Film Condensation:
- Film condensation occurs when a thin film of liquid forms on the cooled surface.
- It is characterized by a continuous and uniform layer of condensate on the surface.
- The condensate film may be thin or thick, depending on the rate of condensation and the properties of the vapor and surface.
- Film condensation is commonly observed in vertical surfaces, such as the inside of a vertical tube or the outside of a vertical plate.

2. Dropwise Condensation:
- Dropwise condensation refers to the formation of discrete liquid droplets on the cooled surface.
- In this mode, individual droplets form and grow, eventually detaching from the surface due to gravity or other forces.
- Dropwise condensation is characterized by isolated droplets rather than a continuous film of condensate.
- This mode is generally observed on hydrophobic or specially coated surfaces, where the droplets do not coalesce and spread as a film.
- Dropwise condensation is more efficient than film condensation, as it reduces the resistance to heat transfer and allows for higher heat transfer rates.

It is important to note that both film and dropwise condensation can occur simultaneously, depending on the conditions and the surface properties. The behavior of condensate on a surface is influenced by factors such as surface roughness, surface tension, vapor properties, and gravity.

In summary, there are two distinct modes of condensation: film condensation and dropwise condensation. Film condensation involves the formation of a continuous film of condensate on the surface, while dropwise condensation is characterized by the formation of discrete droplets. These modes have different heat transfer characteristics and are influenced by various factors.