Yes, as you may have a left-sided hairline or right, and whether hair loss is immenent is also genetic.
50 percent of people have a straight hairline
This is homework. Wiki won't help you cheat. Get to work.
Perfectly. If not, it is not straight.
Depends. Probably not because nothing is perfect! :) i have to disagree - the sides of crystals are straight ~~~ *Sigh* All lines are straight. A man-made one may not be, but by the correct...