共有8个子集，分别为：空集、{a}、{b}、{c}、{a,b}、{a,c}、{b,c}、{a,b,c}
集合A={a,b,c}的所有子集有{a,b,c},{a,b},{a,c},{b,c},{a},{b},{c},∅,共8个.
{a,b,c}{a,b} {b,c} {c,a}{a} {b} {c}空集
