Why do ADCs go down the road in LOL Why does the mid laner have to be a long range AP and why are the top lanes usually meatier? Why is it necessary to have a wild card?

1: ADC is not impossible to go to other roads, mainly in the lower road has a small dragon, more people can quickly take the dragon; ADC is generally very brittle, must be protected, the lower road troop line is long, suitable for the development of ADC and auxiliary 2: single mage is the most important need for the development of the single, single troop line is short, you can let the mage quickly up, and can participate in the dragon group, from the blue BUFF near 3; the team generally have meat, the upper single can say is the best development, the field is generally unwilling to go to catch, this time will let the meat to go to the upper road development, in the late stage of the group so that someone to absorb the damage 4: the field is the core of the whole team, the early stage is completely rely on the field's tempo, which is not comparable to the low-end game, and the main route to let out, you can give their own teammates a better development