PTE Listening MC Single: Which of the following statements is true about the use of contour lines in map-making?

Which of the following statements is true about the use of contour lines in map-making?

• A.They were first used on Ordnance Survey maps.
• B.Land contour lines were first used on a map of France.
• C.Contour lines originally had a military purpose.
• D.Before the 16th century, they were used to show hills, valleys, and rivers.