Choose the correct plural form

shelf

• shelfs

• shelves

• shelvs

• shelfes

postcard

• postcards

• postscards

• postcardes

• postscardes

university

• universities

• universitys

• universitis

• universityes

editor-in-chief

• editors-in-chiefs

• editors-in-chieves

• editors-in-chief

• editor-in-chiefs

difficulty

• difficultys

• difficulties

• difficultyes

• difficultis

watch

• watches

• watchs

• watchies

• watchis

louse

• louses

• lousis

• lice

• lices

stimulus

• stimuluses

• stimuli

• stimulis

• stimulies

belief

• believes

• beliefes

• believs

• beliefs

stepfather

• stepfathers

• stepsfather

• stepsfathers

• stepesfathers