根据语境，用方框中所给短语的适当形式填空。（每个短语仅使用一次）

    When people talk about the future, we like to think that we will be able to drive out of our garages and take to the skies in our own personal flying car. The advantages are obvious. Some people predict this technology {#blank#}1{#/blank#} complete freedom of movement. We could fly at 480 kilometres per hour,{#blank#}2{#/blank#}traffic lights, busy roads and speeding tickets. However, some people point to the disadvantages of flying cars. They say that there are certain to be problems with traffic control. Another big problem is engine{#blank#}3{#/blank#}. What will happen if the car goes wrong? Also, if they become popular, there is {#blank#}4{#/blank#} to be another big problem: air traffic jam. So we may find flying cars {#blank#}5{#/blank#} with more than a few problems if they are to get off the ground!