The first sentence type Rachel should use is simple sentences because they are clear and straightforward, making instructions easy for her younger brother to understand without confusion.
The second sentence type Rachel should use is compound sentences because they can connect related ideas, allowing her to provide more information while still maintaining clarity. This helps to explain the task in a way that is engaging and easier to follow.
Using these two types of sentences will ensure that the instructions are both accessible and informative for her younger brother.