生物与生物之间的关系有( )
A.捕食
B.合作
C.竞争
D.寄生
生物与生物之间的关系,最常见的是捕食关系;其次还有竞争、合作、寄生等其他关系,A、B、C、D都正确.
故选:ABCD.
An analyst does research about difference between an option-free bond and a callable bond. Compared to an otherwise identical option-free bond, a callable bond is least likely to have:()
A. a more uncertain cash flow pattem.
B. less price appreciation potential as interest rates fall.
C. more price depreciation potential as interest rates rise.
简述我国50年代初期民歌合唱获得蓬勃发展的条件与原因。