Adhesion can be defined as the process of attachment of a substance on the surface another. This attachment can be because of the physical or chemical linkage. The physical adhesion can be reversed using enough force.
Among the given options, the water droplets sticking to a window represents the process of adhesion. The water droplets are attached to the surface of the glass. The water forming a large drop is example of cohesion. The water evaporating from leaf is an example of evaporation, and the water falling from the sky is an example of condensation.
Hence, the correct answer is option (A) - water droplets sticking to a window.