Step 1: Find the phrase in statement 3 that points back to an earlier statement.
Statement 3 opens with 'In order to give prominence to these internal relations...' The words 'these internal relations' only make sense if some earlier statement has already named internal relations. Statement 2 does exactly this: 'Structure of proposition stands in internal relations to one another.' So statement 2 must come immediately before statement 3, giving the fixed pair 2-3.
Step 2: Eliminate any option that breaks this 2-3 pair.
Option A (1-2-3-4) actually does keep 2 and 3 together as the second and third terms, so it is not eliminated by this check alone; keep it in mind and check further. Option C (4-3-1-2) does not have 2 immediately before 3, since 3 is preceded by 4 here, so option C is ruled out at this step. Option D (2-1-3-4) places 1 between 2 and 3, breaking the required pair, so option D is also ruled out.
Step 3: Check where statement 4, the idea of operation, should sit.
Statement 4 says, 'An operation is the expression of a relation between the structures of its result and of its bases.' This is the sentence that first properly introduces and defines the term operation in a general sense. Since statements 1 and 3 both use the word operation in a way that assumes the reader already knows what it means (statement 1 talks about 'the operation,' with the definite article, and statement 3 says 'an operation that produces it,' treating the concept as already available), statement 4 should logically come before both 1 and 3, introducing the concept first. This means statement 4 should be the opening statement of the paragraph, which immediately makes option A (1-2-3-4) and option B (2-3-4-1) both look wrong, since neither starts with 4.
Step 4: Assemble the full order starting from 4.
Starting with statement 4, defining operation in general terms, the paragraph then needs to connect to propositions. Statement 3 talks about representing a proposition as the result of an operation, which links directly back to the general definition given in statement 4. So 4 is followed by 3, giving 4-3. Looking at what follows 3, statement 1 explains that the operation is what has to be done to one proposition to make another out of it, which unpacks the mechanism just described in statement 3, so 3 is followed by 1. Finally, statement 2 wraps up by stating the general principle that the structure of a proposition stands in internal relations to others, tying back to why representing propositions via operations in statement 3 made sense in the first place. This gives the full order 4-3-1-2.
Step 5: Confirm this is one of the given choices.
Option C reads exactly 4-3-1-2, matching the order built in Step 4.
Step 6: Why the other options fail.
Option A (1-2-3-4) opens with statement 1, which uses 'the operation' with a definite article, assuming operation has already been defined, so it cannot be the very first sentence. Option B (2-3-4-1) puts statement 4 in the third position, after already discussing internal relations and prominence in 2 and 3, but statement 4 reads as a foundational definition, which fits better as an opener than as a mid-paragraph addition. Option D (2-1-3-4) breaks the mandatory 2-3 pair identified in Step 1 by inserting statement 1 between them.
Final Answer:
The coherent order is 4-3-1-2.
\[ \boxed{\text{Option C: } 4\text{-}3\text{-}1\text{-}2} \]