Explanation:

Only statements 1&2 are correct.

• Thawing permafrost in the Arctic could unlock toxic waste buried for decades.

Permafrost

• Permafrost is any ground that remains completely frozen 32°F (0°C) or colder for at least 2 years straight.

• These permanently frozen grounds are most common in regions with high mountains and in Earth’s higher latitudes near the North and South Poles.

• Permafrost can be found on land and below the ocean floor.

• It is often found in Arctic regions such as Greenland, the U.S. state of Alaska, Russia, China, and Eastern Europe.

• It is found in mountainous regions such as the South American Andes and New Zealand's Southern Alps, as well as below Antarctica.

• Permafrost is made of a combination of soil, rocks and sand that are held together by ice.

• Near the surface, permafrost soils contain large quantities of organic carbon leftover from dead plants that couldn’t decompose due to the cold.

• A layer of soil on top of permafrost does not stay frozen all year.

• This layer, called the active layer, thaws during the warm summer months and freezes again in the fall.

• Permafrost does not always form in one solid sheet – it is both continuous and discontinuous.

Impacts

• Increase in water levels

• Increased erosion

• Traces of zombie virus that can infect humans have been found preserved in permafrost.

• Co2 and methane released from permafrost could cause global warming.  

Hence option 1st is correct.