题干
—Daniel，could you tell me ？
—Certainly，in Tokyo．（ ）
A：when the 2020 Olympics will be held
B：when will the 2020 Olympics be held
C：where the 2020 Olympics will be held
D：where will the 2020 Olympics be held
答案(点此获取答案解析）
C
0g/cm3，其中NO3-的质量分数为3．1％，2 L该溶液中Ca2+的物质的量约等于 （ ）
