Before coming into any conclusion, first we have to understand a model.
A model is the evidence based representation of general idea of objects,animals or events which can not be visualized directly. The evidence on the basis of which the model is postulated can not be always correct under all conditions.It can be modified and reshaped depending on further investigation on it.
As per this question, a scientist studies a model of a widely accepted theory about the position of planets and the sun. On the basis of his study a model was produced.
From above mentioned ideas about a model it is obvious that the correct answer to the question will be C) understand facts which cannot be easily observed
.