【正确答案】：A1 A2 A3 2B1 2B2 2B3 3C1 3C2 3C3
【题目解析】：
根据矩阵乘法：a11=1×a1+0×b1+0×c1=a1；a12=1×a2+0×b2+0×c2=a2；a13=1×a3+0×b3+0×c3=a3；a21=0×a1+2×b1+0×c1=2b1；a22=0×a2+2×b2+0×c1=2b2；a23=0×a3+2×b3+0×c3=2b3；a31=0×a1+0×b1+3×c1=3c1；a32=0×a2+0×b2+3×c2=3c2；a33=0×a3+0×b3+3×c3=3c3；故BA=