At present nobody understands why these three quarks which are in the proton are bound together.目前还没有人知道质子里面的这三个夸克为什么会结合在一起。Atoms are made up of smaller particles - protons, neutrons and electrons - some of which are made up of even smaller ones, called quarks.原子是由更小的粒子，即质子、中子和电子组成的，其中有些是由更小的叫做夸克的粒子构成的。