__________ IS NOT CLEAR TO RESEARCHERS.A. DID DINOSAURS BECOME EXT...

78. - DE DAP AN THI THU TIENG ANH THPT CHUYEN DHSP HA NOI2011
Tiếng Anh DE DAP AN THI THU TIENG ANH THPT CHUYEN DHSP HA NOI2011

78. __________ is not clear to researchers.

A. Did dinosaurs become extinct

B. Why dinosaurs having become extinct

C. Dinosaurs became extinct

D. Why dinosaurs became extinct