Answer:
I'm pretty sure the answer is A
<span>When the surface layer was dug up, the permafrost was exposed. When the weather warmed, this exposed permafrost would have melted and become soggy, causing the ground underneath the tracks to shift.</span>
<span>''Science is the </span>study<span> of the </span>world around<span> us''.</span> The steps are explore, ask questions, and formulate a response to what your making and observation of.