题目

 Mr Zhang is always __ others. People around our neighbourhood all like him very much.      A. ready to helping   B. ready help   C. ready helping     D. ready to help 答案：D已知P是直线3x+4y+8=0上的动点，PA，PB是圆x2+y2-2x-2y+1=0的两条切线，A，B是切点，C是圆心，那么四边形PACB面积的最小值为    ．