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No meson has charge $q=+1$and strangeness $S=−1$ or charge$q=−1$ and strangeness.$S=+1$

The up, charm and top quarks and charge$q=2/3$ and the down, strange and bottom quarks have charge $q=−1/3$. The anti quarks have negative charges with magnitude same as those of the respective quarks. Only the strange quark has strangeness$S=−1$ and the anti strange has strangeness.$S=1$ The rest of the quarks have zero strangeness.

A meson is made up of one quark and one anti-quark. For a meson to have strangeness,$S=−1$it must have a strange quark. The accompanying anti-quark can be anything except an anti-strange. If the anti-quark is an anti-up, anti-charm or anti-top, the net charge of the meson will be.$−\frac{2}{3}−\frac{1}{3}=−1$If the anti-quark is an anti-down or anti-bottom the net charge of the meson will be.$\frac{1}{3}−\frac{1}{3}=0$Thus, charge $q=+1$and strangeness $S=−1$ is not possible.

For a meson to have strangeness$S=1$, it must have an anti-strange quark. The accompanying quark can be anything except a strange quark. If the quark is a up quark, a charm or a top, the net charge of the meson will be$\frac{2}{3}+\frac{1}{3}=1$. If the quark is a down or a bottom the net charge of the meson will be$−\frac{1}{3}+\frac{1}{3}=0$. Thus, charge$q=−1$ and strangeness is $S=+1$not possible.