[解析]
(1)细节理解题。根据第三段中的They need to work out exactly how much energy will be generated in the first drop.This energy is called potential energy(势能). (他们需要精确计算第一次下冲会产生多少能量。这种能量叫做势能。)可知,过山车的能量来自于第一次下冲产生的势能。故选D。
(2)推理判断题。根据第三段Next,the engineers must figure out how much energy each of the following twists and turns will use.This is called kinetic energy(动能).It's important work.If the engineers work out wrongly,the roller coaster may run backward and get stuck in the middle of the track!(接下来,工程师们必须计算出以下每一个曲折都会消耗多少能量。这叫做动能。这是一项重要的工作。如果工程师计算错误,过山车可能会倒退并卡在轨道中间!)以及上下文可知,过山车工程师需要精确计算,所以这份工作对工程师要求是很高的。故选C。
(3)代词指代题。根据第四段中的Nobody wants the roller coaster to get stuck,but it can happen.On rare occasions,a strong wind or a heavy load of passengers may slow the roller coaster just enough to stop it from climbing the next hill. (没有人希望过山车卡住,但这是可能的。在极少数情况下,强风或重载乘客可能会使过山车减速,足以阻止它爬下一座山。)可知,本段主要讲有些情况可能会使过山车卡住,再结合语境可知,后文this应指代过山车卡住这种情况。故选A。
(4)标题归纳题。根据最后一段As long as people are looking for a thrill (刺激),roller coasters will be there to give it to them.Hiding against the force of gravity provides a great feeling that is hard to beat.For many people,roller coasters are the ultimate thrill ride.(只要人们在寻找刺激,过山车就会在那里给他们。躲避地心引力的作用给人一种难以抗拒的感觉。对许多人来说,过山车是终极刺激之旅。)以及前文可知,全文通过对过山车的利用地心引力由势能转换成动能的原理进行了讲解,体现了地心引力的有趣之处。因此A项Gravity can be fun(重力很有趣)概括文意,可以作为本文标题,故选A。