The correct answer is spot.
A spot is a small area of land or water. It can be used to refer to a specific location, such as a picnic spot. It can also be used to refer to a small amount of something, such as a spot of rain.
A plot is a piece of land that is used for a particular purpose, such as farming or building. It can also be used to refer to the plan or outline of a story.
A scene is a particular place or situation. It can also be used to refer to a short section of a play or film.
A landscape is a picture or description of a natural scene. It can also be used to refer to the general appearance of a piece of land.
In the context of the question, the word “spot” is the most appropriate choice because it refers to a specific location that is suitable for a picnic. The other options are not as specific and could refer to a variety of different things.