The correct answer is option 3, the United Kingdom. The United Kingdom was the first country to officially declare a climate emergency. The declaration was made on May 1, 2019, by the UK Parliament after weeks of protests by climate activists from the group Extinction Rebellion. This declaration was significant as it recognized the urgent need to take action to combat climate change and its devastating impacts.

Option 1, Sweden, is not the correct answer as they declared a climate emergency in 2019, but after the UK had already made their declaration.

Option 2, New Zealand, is also not the correct answer as they declared a climate emergency in December 2020, well after the UK.

Option 4, Ireland, is not the correct answer either as they declared a climate emergency in May 2019, but again, after the UK had done so.

Therefore, the correct answer is option 3, the United Kingdom, as they were the first country to declare a climate emergency.