Based on the principle of superposition, in any layered sequence of rocks, the layers at the bottom are older than those at the top. Since Layer M is determined to be 110 million years old, any layers above it must be younger than 110 million years. Thus, if Layers T, R, X, and G are above Layer M, they would all be younger than 110 million years.
Therefore, the correct response is:
Layers T, R, X, and G are all younger than 110 million years.