专科单招什么意思？与统招什么区别?

哲学的基本问题是（ ）

A.社会和自然的关系问题
B.思维和存在的关系问题
C.政治和经济的关系问题
D.理论和实践的关系问题

下列命题中正确的为（）

A.若xo为f(x)的极值点，则必有，f'(xo)=0
B.若f'(xo)=0，则点xo必为f(x)的极值点
C.若f'(xo)≠0，则点xo必定不为f(x)的极值点
D.若f(x)在点xo处可导，且点xo为f(x)的极值点，则必有f'(xo)=0

First,the spotted owl was threatened by logging in the Pacific Northwest．Now it's in danger from a new enemy,the barred owl．Barred owls have been moving to the Northwest from the eastern part of the United States．Stan Sovern has studied spotted owls．Now when he calls for spotted owls,barred owls are starting to appear．Sovern threw a mouse on the ground,and a barred owl grabbed it.
Scientists have learned that spotted owls start to vanish when barred owls come．Some barred and spotted owls have mated and produced hybrid babies．One spotted owl was killed by a barred owl.
Professor Ned K．Brown of the University of California-Berkeley says,"In some areas of Washington,the barred owls moved into very dense,deep woods．The same kind of woods that arc opened up,or destroyed by logging,that adversely influences the spotted owls."
Ten years have passed since the federal government began protecting the spotted owl．Loggers were forced to limit logging on seven million acres of government land．No one is sure how the arrival of the barred owls will impact laws that protect spotted laws．The barred owls like to live in the deep forests where loggers like to cut down trees．The barred owls will likely keep migrating to the Northwest.

When Stan Sovern calls the spotted owl,__.

A.a mouse appears
B.the spotted owl ignores him
C.no one answers
D.barred owls appear