下列说法中正确的是

如图所示，手指施加8N的力把图钉压入木板．若图钉帽的受力面积是1.0×10^﹣4m²，则手指对图钉帽的压强为____Pa．图钉尖制作得很尖锐，是为了在压力一定时，通过减小受力面积来达到____的目的．

    My name is John Brown. I am a school boy. My school is 1my home. Every day it takes me a lot of time 2 there. The road is not good, so I can't 3my bike to school. I often take a bus there. It usually 4 me forty minutes to get there 5.I 6 at seven every morning. I have no time for breakfast at home. I often have something for breakfast on the bus 7 at school. I don't want to  8school. Some students in our school take buses to school. Some students walk to school 9 their homes are not far.10students ride bikes

如图,AB是⊙O的切线, B为切点,AO的延长线交⊙O于C点,连接BC,若$\angle A=30°$,$AB=2\sqrt{3}$,则AC等于(    )