$\begin{array}{l} Z = \left( {1;2} \right) \Rightarrow 1 < x < 2\\ Y = \left[ {1;2} \right) \Rightarrow 1 \le x < 2\\ \Rightarrow Z \subset Y\\ X = \left[ {1;2} \right] \Rightarrow 1 \le x \le 2\\ \Rightarrow Y \subset X\\ \Rightarrow Z \subset Y \subset X\\ \to B \end{array}$
