Describe, in words, the level surface f(x, y, z) = x2/9 + z2 = 1. A cylinder of elliptical cross-section, centered along the Z-axis and crossing the y-axis at y = plusminus 81. A cylinder of elliptical cross-section, centered along the Z-axis and crossing the Z-axis at z = plusminus 0. A cylinder of elliptical cross-section, centered along the Z-axis and crossing the Z-axis at z = plusminus 1. A cylinder of elliptical cross-section, centered along the Z-axis and crossing the Z-axis at z = plusminus 3. A cylinder of elliptical cross-section, centered along the Z-axis and crossing the X-axis at x = plusminus 9.