The given collection of statements appears to correlate trees and global warming. Statements 4 and 3 form a logical block since they emphasize the significance of trees. The author states that trees help in reducing carbon dioxide while burning trees leads to the release of carbon dioxide {'it' in statement 3 refers to carbon dioxide}. Statements 2 and 1 form a pair since 2 introduces a general belief and 1 mentions a 'popular response' to the same. People respond to the news about the increase in temperatures (due to global warming) by suggesting that we should plant more trees. The statement pair 4-3 then justifies this familiar exhortation. Hence, the correct arrangement is 2143.