23. Every Monday morning, all the teachers and students in our school stand at ____ as our national flag is raised.
| A．attention | B．attentions | C．at ease | D．Attentively |
________ the earth to be flat, many feared that Columbus would fall off the edge of the earth.
| A．Having believed | B．Believing |
| C．Believed | D．To believe |
People spend many years learning about favorite sports and ________ how to do them well.
| A．practice | B．practiced |
| C．practicing | D．to practice |
In April, thousands of holidaymakers remained ________ abroad due to the volcanic ash cloud.
| A．sticking | B．stuck |
| C．to be stuck | D．to have stuck |
Today we have chat rooms, text messaging, emailing ... but we seem ________ the art of communicating facetoface.
| A．losing | B．to be losing |
| C．to be lost | D．having lost |
The engine just won't start.Something seems ________ wrong with it.
| A．to go | B．to have gone |
| C．going | D．having gone |