1．（5分）（2008•山东）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
2008 高考数学第 1 题答案解析
2008_退役省自主命题 (2008·理)
2008_退役省自主命题 (2008·理)
1．（5分）（2008•山东）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