【正确答案】 D

【答案解析】[解析] bold(印刷术)粗体字的：The head words in this dictionary are in bold type. dark暗的，黑暗的；深色的，黑色的：It was very dark inside. dense密集的，稠密的，浓密的：The crowd was so dense we could hardly move. black黑色的，黑暗的：It was a cold, black night. 句意：这篇文章里的所有关键词都由黑体字出现，以便引起读者的注意。