下载APP
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】How much sleep does a person need (31) the physiological bases of the need for sleep remain conjectural (猜想), rendering conclusive answers to this question impossible, much evidence has been gathered...
A.
unless
B.
however
C.
although
D.
even if
【单选题】How much sleep does a person need?【B1】the physiological bases of the need for sleep remain conjectural(猜想), rendering conclusive answers to this question impossible, much evidence has been gathered on...
A.
As
B.
Despite
C.
While
D.
Whether
【单选题】How much sleep does a person need (31) the physiological bases of the need for sleep remain conjectural (猜想), rendering conclusive answers to this question impossible, much evidence has been gathered...
A.
extend
B.
range
C.
alter
D.
rise
时，
时，
时，
时，