Question

if the singular ends in consonant +y, the plural is made by changing y to i and adding-es
A baby -babies
A lady - ladies

Answer 1

This rule is the same for any other parts of speech:

adjective: happy - happier - the happiest

verbs: to try - he tries - he tried; to supply - he supplies - he supplied
However, when we use the verb at gerund or present participle (ending in -ing) this rule does not apply. Ex: trying; flying; simplifying; supplying