题目3单选题
若集合A={1,{1},{2},{1,2}},则下列表述正确的是A. {1,2}<img src="https://tihai-oss-cloud.itihey.com/img/66396b9ef10dc4b1f8d5a58967bb120a.webp">AB. {2}<img src="https://tihai-oss-cloud.itihey.com/img/0638b29507bd61d6b1a3e83a7184a8dd.webp">AC. 2<img src="https://tihai-oss-cloud.itihey.com/img/66396b9ef10dc4b1f8d5a58967bb120a.webp">AD. <img src="https://tihai-oss-cloud.itihey.com/img/dd76bb01534c634e290167c1446b26fb.png">