A:生成物中有单质
B:反应前后氧元素的化合价不变
C: 中硫元素的化合价为+2价
D:参加反应的 和 的质量比为17:24
看图片完成对话。
A: When is your birthday?
B: My birthday is on____.
A: What will you do on your birthday?
B: I'll ____.
A: Cool! When is your mother's birthday?
B: It's on____.
A: What will you do for your mother?
B: I'll____.(为她做蛋糕)
A: Great!
Bob ____________ beef, fish ____________ onions.
解释下列的字词。
①疑:____
②呼:____