下午碰到熟人怎么打招呼:
A：Bye .
B：Good afternoon
—I have trouble learning math this term.
—You should pay more _______ to your teacher's advice.
25℃时，水的电离达到平衡：H2OH++OH-；△H>0，下列叙述正确的是（ ）
— ________! Let's ask the twins to go together.
H++OH-；△H>0，下列叙述正确的是（ ）