Steps must be taken _____ this kind of disaster will never happen again.
19. Russia is a country which extends across _____ .
20. "What can I do for you?" or "May I help you?" is a pet phrase used by _____ .
21. Move a few steps, and the oil-paintings look better ______.
22. In fact, the untruthful words made ____ on me. You must answer for that.
23. Every Monday morning, all the teachers and students in our school stand at ____ as our national flag is raised.