Choose the appropriate word(s) from the bracket [lead poisoning, zero, phosgene, dependent, cancer…

Choose the appropriate word(s) from the bracket [lead poisoning, zero, phosgene, dependent, cancer, independent, diethyl ether, first, ethyl carbonate, ethene]: The dehydration of ethyl alcohol with conc. $\text{H}_2\text{SO}_4$ at $140^\circ\text{C}$ mainly yields ____ while at $170^\circ\text{C}$ the main product formed is ____.