阅读短文，判断下列各题的正（A）误（B）
Earthquakes (地震) are one of the most violent and terrible kinds of natural disasters (灾难). We cannot
prevent them, and we don't know when they will happen. This makes earthquakes very dangerous. Recently,
there have been big earthquakes in China, Japan, India, and El Salvador.
What causes earthquakes? Well, all the countries and oceans of the earth are sitting on large plates (板块)
around the earth. These plates fit together like a big puzzle (拼图), and they move around. Earthquakes happen
when two plates move against each other. The earth moves up and down, like an ocean wave.
We don't know when earthquakes will happen, but we can do some things to keep safe. We can make tall
buildings and houses stronger. And we can teach people what to do if there is an earthquake. This way, we
can make these natural disasters just a little bit less terrible.
( )1. Earthquakes happen because there are too many human being's activities.
( )2. Even if we are careful enough, we don't know when earthquakes will happen.
( )3. The reason why earthquakes happen is known to us.
( )4. Only by making tall buildings and houses stronger, can we keep safe in the earthquake.
( )5. The passage is only about the ways to fight against earthquakes.
Z (g)＋R (g) ⊿H<0 的气体反应速率（υ）与时间（t）的关系，t1时开始改变条件，则所改变的条件符合曲线的是