Bad luck! I ________ the sidewalk when an Audi cut in and knocked me down.—You can never be too careful!

28He is too careful _____ his money; he never buys a drink for us

Every Monday morning, students in our school would stand at attention, watching the national flag ______

It was not until dark he found that it was the correct way to solve the problem.

Recent years have________ rapid changes of my hometown.——Yes, I could hardly recognize it when I arrived yesterday.