Final answer:
Regular plural nouns are most often created by adding -s to the singular form. Exceptions include changing -y to -ies, or -f to -ves in certain cases. Possessive forms of plural nouns not ending in -s add 's, while gender-specific suffixes and spelling changes depend on the word structure. The correct answer is option d.
Step-by-step explanation:
Regular plural nouns in English are typically formed by simply adding -s to the end of the singular noun. For instance, if the singular noun is 'book', the plural would be 'books' by adding an 's' at the end. However, English language has exceptions to this rule. For example, when a singular noun ends in -y, we change the 'y' to 'ies' for the plural form, as in 'sky' becomes 'skies'. Similarly, some nouns ending in -f or -fe change these endings to -ves, such as 'leaf' to 'leaves'. Additionally, nouns that don't end in -s but are plural, such as 'children' or 'people', form the possessive by adding 's, which results in 'children's' or 'people's'.
When we encounter a noun that ends in a suffix like -er, -or, or -ess, it typically denotes gender. By adding -ess to a stem that already includes -er or -or, you sometimes get a deletion of a letter, as in 'waiter' where the 'e' is dropped to form 'waitress', and 'actor' where the 'o' is dropped to form 'actress'. The -ess suffix typically denotes a feminine form of the noun.
Word endings can also dictate how a noun is altered when suffixed. For example, when adding -ed to a verb to form its past tense, the pronunciation can change. This suffix can sound like [d], [id], or [t], depending on the final sounds of the verb root. Additionally, some nouns may appear to be plural due to an -s at the end, such as 'mathematics' or 'physics', but they are actually singular and should take a singular verb unless they refer to multiple instances of the subject at hand.