1. If the set $A = \left\{ i , i ^ { 2 } , i ^ { 3 } , i ^ { 4 } \right\}$ (where $i$ is the imaginary unit), $B = \{ 1 , - 1 \}$, then $A \cap B$ equals A. $\{ - 1 \}$ B. $\{ 1 \}$ C. $\{ 1 , - 1 \}$ D. $\phi$
1. If the set $A = \left\{ i , i ^ { 2 } , i ^ { 3 } , i ^ { 4 } \right\}$ (where $i$ is the imaginary unit), $B = \{ 1 , - 1 \}$, then $A \cap B$ equals\\
A. $\{ - 1 \}$\\
B. $\{ 1 \}$\\
C. $\{ 1 , - 1 \}$\\
D. $\phi$