Hex-3-yne is treated with (i) Na in liquid $\mathrm{NH}{}_3$; (ii) mCPBA; (iii) aqueous $\mathrm{H}{}_3\mathrm{O}{}^{+}$ (anti opening of the epoxide). The product is

(i) gives (E)-hex-3-ene; (ii) syn epoxidation gives the trans epoxide; (iii) anti ring opening is overall anti addition of two OH to an E alkene, which gives the meso diol (as anti addition of $\mathrm{Br}{}_2$ to a trans alkene gives a meso dibromide).