You will be given a definition of a task first, then some input of the task.
In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: A parameter of great importance in chromatography is the equivalent height of theoretical plate (H). The van Deemter equation describes the behavior of a filler column for gas-liquid chromatography, where H = A + (B / u) + Cu, so that:
Options: <1> C is the parameter that is taken as a measure of the quality of the filling of the column. <2> A is the coefficient that collects the contribution of longitudinal diffusion. <3> B is the parameter that is related to the resistance to the transfer of matter that opposes the stationary phase. <4> u is the linear velocity of the mobile phase. <5> B is canceled in columns without filling.
Output:
4