1.满足 $M \subseteq\left\{a_{1}, a_{2}, a_{3}, a_{4}\right\}$ ,且 $M \cap\left\{a_{1}, a_{2}, a_{3}\right\}=\left\{a_{1}, a_{2}\right\}$ 的集合 $M$ 的个数是 )
参考答案B
2008_退役省自主命题 (2008·文)
1.满足 $M \subseteq\left\{a_{1}, a_{2}, a_{3}, a_{4}\right\}$ ,且 $M \cap\left\{a_{1}, a_{2}, a_{3}\right\}=\left\{a_{1}, a_{2}\right\}$ 的集合 $M$ 的个数是 )
【答案】B
【解析】解析:本小题主要考查集合子集的概念及交集运算。集合 $M$ 中必含有 $a_{1}, a_{2}$ ,则 $M=\left\{a_{1}, a_{2}\right\}_{\text {或 }} M=\left\{a_{1}, a_{2}, a_{4}\right\}$ 。选B.