A:该气体中肯定含有H2S和SO2
B:该气体中肯定含有SO2
C:该气体中肯定含有CO2和SO2
D:该气体中肯定含有H2S、CO2和HI
— _______ are you going to the School Uniform Exhibition, Amy?— To learn about different styles of school uniforms.
设Sn=a1+a2+L+an,其中Sn为数列的前n项和,已知数列{an}的前n项和Sn=5n2+1.该数列的通项公式.
植物种子的寿命有长也有短,短的几小时,长的几年,超过____年已算长命的了。