Given sets $A = \{ x \mid x < 1 \} , B = \left\{ x \mid 3 ^ { x } < 1 \right\}$, then A. $A \cap B = \{ x \mid x < 0 \}$ B. $A \cup B = \mathbf { R }$ C. $A \cup B = \{ x \mid x > 1 \}$ D. $A \cap B = \varnothing$
Given sets $A = \{ x \mid x < 1 \} , B = \left\{ x \mid 3 ^ { x } < 1 \right\}$, then
A. $A \cap B = \{ x \mid x < 0 \}$
B. $A \cup B = \mathbf { R }$
C. $A \cup B = \{ x \mid x > 1 \}$
D. $A \cap B = \varnothing$