用所给短语的适当形式填空
in the sixth century,according to,fall into,by accident,in this way
1.------the passage,I understood this sentence.
2.Tea,the most popular drink in the world(after water),was invented------.
3.------,he worked out that math problem.
4.He was so careless that he------the river when he went across the bridge yesterday.
5.The abacus was invented------by the Chinese.