𝗖𝗵𝗼𝗼𝘀𝗲 𝘁𝗵𝗲 𝗰𝗼𝗿𝗿𝗲𝗰𝘁 𝗼𝗽𝘁𝗶𝗼𝗻.
The Arctic is one of the last places on Earth that is still a ___________ and a _____________.

• mystery, challenge
• secret, mysterious
• challenging, mystery
• mystery, challenging