\[\boxed{\mathbf{1.}}\]
\[1)\ 20,\ 30,\ 40,\ 50,\ 60,\ 70,\ 80,\ 90,\ \]
\[100.\]
\[2)\ 21,\ 22,\ 23,\ 24,\ 25,\ 26,\ 27,\ 28,\ \]
\[29,\ 30.\]
\[3)\ 90,\ 80,\ 70,\ 60,\ 50,\ 40,\ 30,\ 20,\ \]
\[10.\]
\[4)\ 90,\ 89,\ 88,\ 87,\ 86,\ 85,\ 84,\ 83,\ \]
\[82,\ 81,\ 80.\]