Read this excerpt from Immigrant Kids, by Russell Freedman. Now the examinations began. First the immigrants were examined by two doctors of the United States Health Service. One doctor looked for physical and mental abnormalities. When a case aroused suspicion, the immigrant received a chalk mark on the right shoulder for further inspection: L for lameness, H for heart, X for mental defects, and so on. The second doctor watched for contagious and infectious diseases. He looked especially for infections of the scalp and at the eyelids for symptoms of trachoma, a blinding disease. Since trachoma caused more than half of all medical detentions, this doctor was greatly feared. He stood directly in the immigrant's path. With a swift movement, he would grab the immigrant's eyelid, pull it up, and peer beneath it. If all was well, the immigrant was passed on. Which detail best supports the idea that only immigrants with good health were allowed entrance into the United States?

A. One doctor drew chalk marks on immigrants with health problems.

B. The two doctors worked for the United States Health Service.

C. An H mark on an immigrant meant he or she had heart problems.

D. Trachoma is a blinding and very contagious eye disease.