The earth was:
Aonce thought to be flat
Bthought once been flat
Conce flat to be
Donce think to be flat

Aonce thought to be flat
Bthought once been flat
Conce flat to be
Donce think to be flat
Related Questions:
Which pair does not match?
| A. Communicative approach | Focus on fluency | 
| B. Grammar Translation method | Real life communications | 
| C. Suggestopedia | The use of music | 
| D. Audio lingual method | Pattern drills are important |