41. The quality of gold is indicated by $\mathrm{K}$, pure gold is $\qquad$ , and jewelry with $50 \%$ gold content is $\qquad$ _.
A. $12 \mathrm{~K} 、 6 \mathrm{~K}$
B. $48 \mathrm{~K} 、 24 \mathrm{~K}$
C. $36 \mathrm{~K} 、 18 \mathrm{~K}$
D. $24 \mathrm{~K}, 12 \mathrm{~K}$
【Answer】D
【Analysis】The purity of gold refers to the content of gold, generally indicated by $\mathrm{K}$. The purity of $24 \mathrm{~K}$ gold is the highest, followed by $18 \mathrm{~K}$, and so on. “$\mathrm{K}$” is derived from the French Karat. In the unit of gold purity, $1 \mathrm{~K}$ represents $1 / 24$ or $4.1666 \%$, meaning the gold content is $1 / 24$ or $4.1666 \%$. 18K gold indicates a gold content of $18 / 24$, which is $75 \%$, with the remaining $25 \%$ being other metals; $12 \mathrm{~K}$ gold indicates a gold content of $12 / 24$, which is $50 \%$, with the remaining $50 \%$ being other metals, typically copper, silver, etc., in gold jewelry. The name of gold depends on its purity, for example, gold with a purity of $99 \%$ is called “pure gold”, gold with a purity of $99.9 \%$ is called “thousand pure gold”, gold with a purity of $99.99 \%$ is called “ten thousand pure gold”, and gold with a purity of $99.999 \%$ can be called “hundred thousand pure gold” or “high purity gold”. There is a saying, “Gold is never absolutely pure, and no one is perfect.” In fact, 100\% pure gold does not exist. One reason is the limitations in refining technology, and the other is that gold jewelry or gold bars will inevitably contain other substances during the processing.