truc thang co gi ma hay?nen hay khong?

tuong rang truc thang thi bay duoc .ai ngo dau truc thang cung phai bo vay.
minh tuong rang xay duoc may cai truc thang ra la co the tung hoanh ngang doc .ma ton it thoi gian ,khong can thuyen cung di duoc .nhung ma that la sai lam .no cung giong nhu la quan bo vay thoi.cung phai thuyen tro di .ton thoi gian bang quan bo vay.anh em hay thu nghiem va cho y kien coi
sorry may o quan khong co vietkey.