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A state transition diagram with states $A, B,$ and $C,$ and transition probabilities $p_{1}, p_{2}, \dots, p_{7}$ is shown in the figure (e.g., $\text{p}_{1}$ denotes the probability of transition from state $A$ to $B$). For this state diagram, select the statement(s) which is/are universally true.

1. $p_{2} + p_{3} = p_{5} + p_{6}$
2. $p_{1} + p_{3} = p_{4} + p_{6}$
3. $p_{1} + p_{4} + p_{7} = 1$
4. $p_{2} + p_{5} + p_{7} = 1$