Help me with this question please

Only logical answer would be the third one: A temperate forest became a swamp.

Explanation:

A pond cannot become a lake unless human interaction was involved to dig around the pond and fill it in with water, making it a man made lake.

A forest can't become a desert. Come on.

And finally, and arctic region cannot become a tropical region because it would be too cold for trees, grass, animals (other than local animals like killer whales and polar bears) cannot thrive in the region.

surface modification is a versatile tool and has been widely used in material science and engineering that has significantly facilitated the study and characterization of complex materials. at  matexcel, experienced experts in surface science can offer tailored efforts to meet the specific needs from our clients.

"d.) carbon dioxide and hydrogen sulfide"