1. For training. Among the four statements: "number $a$ is divisible by 2", "number $a$ is divisible by 4", "number $a$ is divisible by 12", "number $a$ is divisible by 24" - three are true, and one is false. Which one?
1. Note that: "number $a$ is divisible by 24" $\Rightarrow$ "number $a$ is divisible by 12" $\Rightarrow$ "number $a$ is divisible by 4" $\Rightarrow$ "number $a$ is divisible by 2". Therefore, only the statement "number $a$ is divisible by 24" can be false.