On the Density Altitude Chart (Figure 8), a point that falls exactly on the diagonal "Standard temperature" line means that —

Why: Figure 8's "Standard temperature" line traces the International Standard Atmosphere (ISA) temperature for each pressure altitude. The Remote Pilot Study Guide defines density altitude as "the altitude in the standard atmosphere corresponding to a particular value of air density" — so whenever the outside air temperature equals the standard temperature for a given pressure altitude, density altitude and pressure altitude are the same value, which is exactly what that diagonal line plots.

• Invents a restriction that doesn't exist on the chart; the standard-temperature line is a reference line within the chart's normal range, not a boundary of it.
• Confuses the chart's separate altimeter-setting conversion table (used to find pressure altitude from field elevation) with the main density-altitude graph, which only needs pressure altitude and outside air temperature as inputs.