Which line from the text best supports this central idea?

A: Before they could be admitted to the United States,
immigrants had to pass through Ellis Island.

B: The immigrants had numbered identity tags pinned
to their clothing.

C: 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.

D: They were allowed to sit and rest and try again.