A.a<0,b<0
B.a>0,b>0
C.a≤0,b>0
D.a≥0,b<0
[单选题]A.a<0,b<0B.a>0,b>0C.a≤0,b>0D.a≥0,b<0
[单选题]A.a<0,b<0B.a>0,b>0C.a≤0,b>0D.a≥0,b<0
[单选题]A.π/5B.π/2C.π/3D.π/4
[单选题]A.①③B.②④C.①④D.③⑤
[单选题]A.2,3,4,5…B.2,4,6,8…C.2,5,8,11…D.3,6,9,12…
[单选题]A.π/5B.π/2C.π/3D.π/4
[单选题]A.π/5B.π/2C.π/3D.π/4
[单选题]A.π/5B.π/2C.π/3D.π/4
[单选题]A.2,3,4,5…B.2,4,6,8…C.2,5,8,11…D.3,6,9,12…
[单选题]A.Ⅰ类洞B.Ⅱ类洞C.Ⅲ类洞D.Ⅳ类洞E.Ⅴ类洞