Step-by-step Solution:

Analysis of the Road Systems

The problem describes two independent sets of parallel roads, and within each set, there are unlinked subgroups.

• 
  North-South Roads (A, B, C, D, E): The clues establish two separate subgroups whose positions relative to each other are unknown.
  
  
  
  • Group 1: B --- (0.5 km) --- C --- (0.5 km) --- A
  
  
  • Group 2: D --- (1 km) --- E
  
  
  
  


• 
  East-West Roads (F, G, ... M): Similarly, the clues for these roads establish two separate subgroups.
  
  
  
  • Group 1: M --(1 km)-- K --(0.5 km)-- L --(0.5 km)-- G
  
  
  • Group 2: I --- (1 km) --- J
  
  
  
  

Evaluation of the Options

• 
  Options A, B, and C: These statements (L vs I, C vs D, I vs K) all attempt to link roads from different, unconnected subgroups. Since their relative positions cannot be determined from the given information, none of these statements can be confirmed as true.
  


• 
  Option D. C and B are 1/2 km apart: This is True. It is a direct restatement of the given clue, "Road B is 1/2 km West of road C."
  

Final Answer: The only statement that is necessarily true is D.