Fact 1: Carbon dioxide concentrations in the air have increased over the last decade dramatically. Fact 2: Carbon dioxide is formed by burning carbon. Given the two facts above, burning carbon concentrations have what?
Options are:
1). Greenhouse gases;
2). Chemical energy;
3). reduced significantly;
4). increased dramatically;
5). Plant growth is reduced;
6). heat energy;
7). shrunk;
8). declined spectacularly;
4).