A:a1+a101>0
B:a2+a100<0
C:a3+a99=0
D:a51=51
—He, together with Tom, _____ going to visit Shanghai in July. How about you?
—I'm afraid I have to stay at home _______
﹣7﹣(﹣21)=____
某种兴奋剂的结构简式如图:
回答下列问题: