In a particular experiment, moving kaon mesons collide with stationary protons. The following reaction takes place
$$p + {K^ - } \to {K^0} + {K^ + } + X$$

where X is an unknown particle. This process involves the strong interaction. The quark structure of the kaons is ${K^ - } = \bar us$, ${K^0} = d\bar s$, and ${K^ + } = \bar us$.

(i) State the strangeness of the unknown particle X.

(ii) Particle X is a hadron. State and explain whether X is a meson or a baryon.

(i) S = -3; 
(ii) baryon;
to conserve baryon number / has structure sss;

(a)(i) a strangeness = -3 was usually correctly given, as was the identification of X as a baryon.