(a)
B and C
The degree of a vertex is the number of edges incident to it. Vertices B and C have odd degree, implying others (A, D, E, F, G, H) are even in context.
Result: Vertices B and C [2]

(b)
For \( x \leq 5 \): \( 33 + 2x \)
For \( x \geq 5 \): \( 38 + x \)
Total road length is \( 33 + x \, \text{km} \). Repeat edge BC (length \( x \)) for \( 33 + 2x \), or repeat path B-A-C (length 5) for \( 38 + x \). Intervals determined by \( 33 + 2x = 38 + x \), so \( x = 5 \).
Result: \( 33 + 2x \) for \( x \leq 5 \), \( 38 + x \) for \( x \geq 5 \) [3]