I (free public/shared bicycles):
Shifts short trips from cars to cycles, directly reducing parking demand.
III (odd–even entry rule):
Immediately cuts car volume by limiting daily access—large short-term relief.
V (build multi-storey/underground parking):
Adds new supply where land is scarce—addresses structural shortage.
X (dynamic parking pricing):
Prices curb/lot spaces by demand to target optimal occupancy, reducing cruising and allocating scarce supply efficiently.
Less effective/orthogonal items: II only manages reservations (redistributes, doesn’t add capacity), IV “prohibitively expensive” is blunt versus calibrated X, VII speculative, VIII relies on voluntary adoption, IX heritage/pedestrianization doesn’t target parking.
Hence the most impactful set is (D).