D．o scientists know how many cryptic species exist?

A．Not yet.

B．Yes, they do.

C．They will know the answer in another one or two years.

D．They will never know the answer.

[单选题]Scientists have many theories about how the universe ___ into being.A． cameB. was comingC． had comeD. would come

[单选题]D．o you know how to study better and make your study more effective(有效率的)? We all know that Chinese students usually study very hard for long (11) ．This is very good，but it doesn't (12)a lot，for an efficient student must have enough sleep，enough foo

[单选题]H．ow many hours of housework did men do every week in the 1970s?A． About 23. B. About 26.C． About 13. D. About y.

[单选题]H．ow many hours of housework did men do every week in the 1970s?A．About 23.B．About 26.C．About 13.D．About y.

[单选题]Most of what Ireally need to know about how to live and what to do and how

[单选题]Most of what Ireally need to know about how to live and what to do and how

[单选题]Most of what Ireally need to know about how to live and what to do and how

[单选题]Most of what Ireally need to know about how to live and what to do and how

[单选题]Most of what Ireally need to know about how to live and what to do and how

[单选题]Most of what Ireally need to know about how to live and what to do and how