The correct answer is option 4: 1, 2, and 3.

Landforms observed on the surface of the Earth are a result of several factors:

1. Differences in the type and structure of the crustal material: The Earth`s crust is composed of different types of rocks, such as sedimentary, igneous, and metamorphic. These rocks have different properties and structures, which can affect the formation of landforms. For example, sedimentary rocks are often eroded more easily than igneous rocks, resulting in different landforms.

2. Differences in the land forming processes: Different processes such as weathering, erosion, deposition, and tectonic activity shape the Earth`s surface. These processes act differently in different areas, leading to the formation of varied landforms. For instance, erosional processes by rivers can create valleys, while tectonic activity can lead to the formation of mountains.

3. Differential rates of the processes at different places on the Earth`s surface: The rate at which the land forming processes occur can vary from one location to another. Factors such as climate, topography, and geological conditions can influence the speed and intensity of these processes. This differential rate of processes contributes to the creation of diverse landforms.

In conclusion