I'm________about what I say because careless remarks are likely to hurt others' feelings.
A:enthusiastic
B:curious
C:doubtful
D:cautious
____
金属汞在加热条件下可以与氧气化合生成氧化汞,反应如下:2Hg +O2= 2HgO ,下列哪个选项可以说明0.2mol Hg 与0.2mol O2充分反应后物质的种类及其量的情况?( )