The question refers to the composition of standard 18-carat gold, which is a type of gold alloy. The term "carat" is used to measure the purity of gold, with 24-carat being 100% pure. Hence, 18-carat gold means it has 18 parts gold to 6 parts of other metals, making it 75% pure gold.
Option 1 is incorrect as it suggests a composition of 82 parts gold, which is higher than 24 and hence, infeasible.
Option 2 is wrong because it suggests an extremely low gold content (18 parts out of 100), which does not match the high purity implied by the term "18-carat gold".
Option 4 is also wrong as it implies a 37.5% gold composition, which is closer to 9-carat gold rather than the 18-carat gold in question.
Therefore, Option 3 is the correct answer as it correctly indicates the composition of standard 18-carat gold: 18 parts gold and 6 parts other metals.