A student is talking to her teacher.
S: I hear that scientists are planning to study asteroids and meteors, right?
T: Yes. They want to determine whether Earth is in danger of being struck by such a rock.
S: What if they discover that a big one is coming straight for us?
T: In that case, there are two things they can do. They can launch rockets to push the rock off its course.
S: So that it will miss Earth, right?
T: Right. And if that fails, we can try destroying the rock with nuclear missiles.
S: Wow! I never thought that nuclear weapons could save the world instead of ending it!

save your breath 别浪费唇舌
asteroid 小行星
I (was) determined to do = made up my mind  
We are in danger of losing the rice crop if it doesn't rain.
What (will/would happen) if...
You can't miss sb/sth. 你不会错的
intersection 十字路口
Let's go picnicking tomorrow. = Let's go on a picnic tomorrow.
He swims like a rock. 游泳象旱鸭子