Câu hỏi:

Cho hai tập hợp \(P = \left\{ {m;\,\,n;\,\,c} \right\}\) và \(Q = \left\{ {5;\,\,6;\,\,7} \right\}\). Hãy viết các tập hợp có \(2\) phần tử thuộc tập hợp \(P\) và \(1\) phần tử thuộc tập hợp \(Q\). 

• A \(\left\{ {m;\,\,n;\,\,5} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,6} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,7} \right\}\,\,;\,\,\,\left\{ {n;\,\,c;\,\,5} \right\}\,\,;\,\,\,\left\{ {n;\,\,c;\,\,6} \right\}\\ \left\{ {n;\,\,c;\,\,7} \right\}\,\,;\,\,\,\left\{ {m;\,\,c;\,\,5} \right\}\,\,;\,\,\,\left\{ {m;c;6} \right\}\,\,;\,\,\,\left\{ {m;c;7} \right\}\)
• B \(\left\{ {m;\,\,n;\,\,5} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,6} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,7} \right\}\,\,;\,\,\,\left\{ {n;\,\,c;\,\,5} \right\}\,\,;\,\,\,\left\{ {n;\,\,c;\,\,6} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,c;\,\,5;\,\,6;\,\,7} \right\}\\ \left\{ {n;\,\,c;\,\,7} \right\}\,\,;\,\,\,\left\{ {m;\,\,c;\,\,5} \right\}\,\,;\,\,\,\left\{ {m;c;6} \right\}\,\,;\,\,\,\left\{ {m;c;7} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,c;\,\,5;\,\,6;\,\,7} \right\}\)
• C \(\left\{ {m;\,\,n;\,\,5} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,6} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,7} \right\}\,\,;\,\,\,\left\{ {n;\,\,c;\,\,5} \right\}\\ \left\{ {n;\,\,c;\,\,6} \right\}\,\,;\,\,\,\left\{ {n;\,\,c;\,\,7} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,c;\,\,5;\,\,6;\,\,7} \right\}\)
• D \(\left\{ {m;\,\,n;\,\,5} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,6} \right\}\,\,;\,\,\,\left\{ {m;\,\,n;\,\,7} \right\}\\ \left\{ {m;\,\,n;\,\,c;\,\,5;\,\,6;\,\,7} \right\}\,\,;\,\,\,\left\{ {m;\,\,c;\,\,5} \right\}\,\,;\,\,\,\left\{ {m;c;6} \right\}\,\,;\,\,\,\left\{ {m;c;7} \right\}\)