Answer:
2.4.1 What do you call a rock that doesn't erode easily? A resistant stratum or a resistant layer. This is a hard or tough layer of rock that can withstand the forces of erosion better than the other layers around it. For example, the feature labelled A is made of quartzite, which is a rock that used to be sandstone but got transformed by heat and pressure. Quartzite is so hard that it can scratch glass and it is mostly made of quartz.
2.4.2 How can you tell the difference between feature A and feature C? Well, they are not the same in how they were formed, what they are made of and how fast they erode. Feature A is a resistant layer of quartzite, which is a metamorphic rock that changed from sandstone because of heat and pressure. Feature C is a less resistant stratum or a less resistant layer. This is a soft or crumbly layer of rock that gets worn away faster than the other layers around it. For example, the feature labelled C is made of shale, which is a rock that came from mud that had clay and quartz in it. Shale is so soft that it can break into thin layers.
2.4.3 Why do slopes P and Q look different? Because they are concave slopes and convex slopes, respectively. A concave slope is a slope that bends inwards or downwards, like a bowl. A convex slope is a slope that bends outwards or upwards, like a dome. Concave slopes usually form on resistant layers that erode slower than the layers below them, creating a ledge or a cliff. Convex slopes usually form on less resistant layers that erode faster than the layers above them, creating a smooth slope or a valley.