A：HCOOH + H2OHCOO－+ H3O+
B：CO2 + H2OHCO3－+ H+
C：CO32－+ H2O HCO3－ + OH－
D：HS－+ H2OS2－+ H3O+
“____,____”的诗句，将“离愁”写得如此真切、深刻。（李煜《虞美人》）
—Who's singing in the park?
—It ________ be Ann. Ann is much taller.
Please____(drink)more water every day.
