Question

Надо изменить во множественное число ))

Biography---
Seaman---
Piano---
Theory---
Discovery---
Library---
City---

Answer 1

Biography--- Biographies
Seaman--- Seamen
Piano--- Pianos
Theory--- Theories
Discovery--- Discoveries
Library--- Libraries
City--- Cities

Answer 2

Biography - biographies;
Seaman - seamen;
Piano - pianos;
Theory - theories;
Discovery - discoveries;
Library - libraries;
City - cities.