The depth of a 7 year old teeth from front to rear compared to their width is Four times as deep.
Option 3 is correct
The depth of the teeth is determined by the thickness of the bone that supports them. In a 7-year-old, the bone is still developing and is relatively thin. This means that the teeth are not as deep as they will be in an adult.
The width of the teeth is determined by the size of the jawbone. The jawbone is also still developing in a 7-year-old, but it is growing at a faster rate than the bone that supports the teeth which means that the teeth are narrower than they will be in an adult.