The bar used for defining the standard metre at the International office of weights and measures at Sevres near Paris, is composed of

• A. 50% platinum and 50% iridium
• B. 60% platinum and 40% iridium
• C. 70% platinum and 30% iridium
• D. 80% platinum and 20% iridium
• E. 90% platinum and 10% iridium