A：a
B：an
C：\
下列有关血管的叙述中，正确的是（ ）
学生的责任来自于( )①老师和家长的命令 ②法律的规定 ③公民身份 ④分配的任务
The plane had already taken off. So he decided ________the G109 Train to Shanghai.
——Would you like tea or coffee?——________ ,thanks. It's hard for me to fall asleep at night after drinking them.
