Concept:
Coherent sentence formation involves identifying the logical subject, the action (verb), and the conditions or qualifiers that follow. In this case, we are looking for a statement regarding the allocation of resources (space) based on a specific rule.
Step 1: Identifying the Subject and Action.
Fragment R (vehicles are allotted space) acts as the main independent clause of the sentence. It establishes what is happening: the distribution or assignment of space to vehicles.
Step 2: Linking the Condition.
Fragment P (depending on) is a participial phrase that must follow the action to explain the criteria for the allocation. It naturally connects the act of allotting space to the rule that governs it.
Step 3: Defining the Rule and Basis.
The rule is S (first-come-first-service), which describes the methodology. Finally, the word Q (basis) acts as the concluding noun that "first-come-first-service" modifies.
Full Sequence: R + P + S + Q
"Vehicles are allotted space depending on first-come-first-service basis."
Final Answer: Option D