The correct answer is option 2, Sweden. Sweden was the host country of the United Nations World Environment Day in 2022.

Option 1, Canada, is not the correct answer. While Canada has hosted World Environment Day in the past, it was not the host country in 2022.

Option 3, South Africa, is also not the correct answer. South Africa has hosted World Environment Day before, but it was not the host country in 2022.

Option 4, Brazil, is also not the correct answer. While Brazil has hosted World Environment Day in the past, it was not the host country in 2022.

Therefore, the correct answer is option 2, Sweden. Sweden was chosen as the host country for the United Nations World Environment Day in 2022.