The alcohol shown is heated with concentrated $\mathrm{H}{}_2\mathrm{SO}{}_4$ at 443 K. Which structure is the major alkene (Saytzeff product, the more stable geometrical isomer)?

The alcohol is butan-2-ol. E1 elimination follows Saytzeff's rule and gives the more substituted alkene, but-2-ene. Of its two geometrical isomers, the trans (E) form is more stable because the methyl groups are far apart, so it predominates over cis-but-2-ene and but-1-ene.