At the beginning of the 20th century, many people thought that the family was falling apart—__________, they thought it was dying. ( )
A:on the other hand
B:for another
C:in other words
D:in addition
今年,我市发现人感染H7N9禽流感病例,该病是由H7N9禽流感病毒引起的,它通常只感染鸟类,少见情况会感染人、猪、马等哺乳动物.专家介绍说:“对于所有的流感,我们都建议两条预防原则:两勤三早.”“两勤”就是勤洗手、勤通风,“三早”就是早发现、早诊断、早隔离治疗.根据上述资料,请回答:
生物学知识是( )
At the start of the 20th century, cars became popular.