Answer:
Third Option: Good chefs bring their own knifes.
It should be "Good chefs bring their own knives.
Step-by-step explanation:
Knife is a noun which is made plural by replacing "fe" with "-ves" i.e "knives" from "knife"
Many nouns end with "f" sound are made plural by adding "-ves" at their end. But there are many other nouns ending with "f" sound but made plural by simply adding "-s" at the end.
There is no hard and fast rule for identifying whether to add "-ves" or simple "-s" and even if some rule is made, there appear many exceptions to such rules. So it is better to learn them by practice.
1: Words ending with -ff are made plural by simply adding -s, e.g;
cliff - cliffs
toff - toffs
scuff - scuffs
sniff - sniffs
2: Some words ending in f are made plural by adding -s in the end, e.g
roof - roofs
chef - chefs
chief - chiefs
oaf -oafs
3: Words which end in f or fe and are made plural by -ves
calf - calves
half - halves
knife - knives
leaf - leaves
loaf - loaves
life - lives
wife - wives
shelf - shelves
thief - thieves
yourself - yourselves
themselves
4: Some words can have both endings -ves or -s, e.g
scarf - scarfs/scarves
dwarf - dwarfs / dwarves
wharf - wharfs / wharves
handkerchief - handkerchiefs / handkerchieves
First and second options correctly use plural nouns.