Which type of rock is mentioned as having lines of weakness that can affect landforms?

Sedimentary rock is correct because it typically forms in layers, and the processes involved in its formation often lead to the development of lines of weakness, such as faults or bedding planes. These characteristics make sedimentary rocks more susceptible to erosion and weathering, which can significantly impact landforms over time. For instance, when sedimentary rocks are subjected to natural forces, these lines of weakness can influence how the rock erodes, leading to the formation of valleys, cliffs, and other geological features.

In contrast, while granite is a type of igneous rock known for its durability and crystalline structure, it generally lacks the layering that creates lines of weakness typical of sedimentary rocks. Siltstone, another sedimentary rock, does possess some features of weakness, but it isn't as broadly representative of sedimentary rocks as a category. Igneous rocks, formed from the cooling of magma, also do not typically exhibit the same linear weaknesses that influence landform development in the same way sedimentary rocks do. Therefore, sedimentary rock is the most accurate answer regarding the type of rock that has lines of weakness affecting landforms.