Why MAYA modeling in time to delete the line can not delete

Why MAYA modeling in time to delete the line can not delete?
There are two points, plus a line between how
who help me thank you ah

first POLYGONS in the modeling, if the 2-point increase in a line can Edit Mesh's Split Polygons Tool that can be two points between the lines.
Line can not delete delete there is a reason for this is because the line connected to a surface, you may wish to observe from the perspective of the next.If it were not for this reason, they immediately clear historical record, once again deleted, because sometimes there is MAYA instability.
patience to do it, at the beginning of times to do some model is entangled ……Come on!