Please help me with this.

It is the fourth option

Explanation:

And should go before "I boasted"

D. to provide information about trachoma and to explain how it was diagnosed among immigrants.

Explanation:

This is the excerpt from Russell Freedman's book "The Immigrant Kids" which tells the story of the life of the kids who immigrated to America in early 20th century.

This particular excerpt tells about the routine check-up they needed to pass before entering the country.

It explains the screening for trachoma, an infectious disease that affects eyelids, causing even blindness. Trachoma is caused by a bacteria and is contagious, so this screening's purpose was to prevent infected kids to spread the bacteria through the country.

The excerpt provides brief information regarding the trachoma and explains the process of diagnosing it among the immigrants.