(1) Given the set $M=\{1,2\}, N=\{2 a-1 \mid a \in M\}$, then $M \cap N=$
(A) $\{1\}$
(B) $\{1,2\}$
(C) $\{1,2,3\}$
(D) Empty set
(1) Prompt: Since $N=\{2 a-1 \mid a \in M\}=\{1,3\}$, then $M \cap N$ $=\{1\}$.