What valuable item did Admiral Sir William
Reginald Hall find in the iron-encased sea
chest?
O a British fishing trawler
O personal papers and nautical charts
O the location of British warships
O a German codebook

D. German code book.

Explanation:

The book contained the code system used by the German military to communicate with their naval leaders abroad.

~Hope this helped! ;)

i think the answer is invented words, rhyming knack, alliteration, and, metaphor.