5.函数f(x)={■(6^x "-" 2"," x>0"," @x+log_6 12"," x≤0)┤的零点之和为

　　A.-1 B.1 C.-2 D.2

6.函数f(x)=cos(3x+π/2)的单调递增区间为

　　A.[π/6+2kπ/3,π/2+2kπ/3](k∈Z)

　　B.[π/6+kπ/3,π/2+kπ/3](k∈Z)

　　C.[-π/6+kπ/3,π/6+kπ/3](k∈Z)

　　D.[-π/6+2kπ/3,π/6+2kπ/3](k∈Z)

7.某几何体的三视图如图所示,则该几何体的体积为

　　A.24π-6

　　B.8π-6

　　C.24π+6

　　D.8π+6

8.已知两个单位向量e1,e2的夹角为60°,向量m=te1+2e2(t<0),则

　　A.("|" m"|" )/t的最大值为-√3/2 B.("|" m"|" )/t的最小值为-2

　　C.("|" m"|" )/t的最小值为-√3/2 D.("|" m"|" )/t的最大值为-2

9.若直线y=kx-2与曲线y=1+3lnx相切,则k=

A.2 B.1/3 C.3 D.1/2