表示
在合成氨反应中，经过2秒，氨的浓度增加了0.4摩尔/升．利用氨的浓度变化表示该反应在这2秒内的反应速率为（ ）．
在合成氨反应中，经过2秒，氨的浓度增加了0.4摩尔/升．利用氨的浓度变化表示该反应在这2秒内的反应速率为（ ）．
“Can your brother and sister understand the English teacher?”“No, _____ of them can.”
“Can your brother and sister understand the English teacher?”“No, \_\_\_\__ of them can.”
已知乙醇分子中的氧原子为18，这种乙醇和乙酸混合加入少量浓硫酸共热，反应后生成的酯的相对分子质量是____．
已知乙醇分子中的氧原子为18，这种乙醇和乙酸混合加入少量浓硫酸共热，反应后生成的酯的相对分子质量是\_\_\_\_．
The dispute is _____ to be settled for a long time to come.
The dispute is \_\_\_\__ to be settled for a long time to come.
On addition, more than one-third of Americans over the age of 25 have a college degree or higher.
On addition, more than one-third of Americans over the age of 25 have a college degree or higher.
The electric shaver _____ before it can be used.
The electric shaver \_\_\_\__ before it can be used.