Easy
Hard-ish
Hard
Easy
Almost imposible
100

Singular noun of an animal with four legs, often called man's best friend.

Dog

100

Plural form of a young child who is not yet a toddler.

Babies

100

Singular form of a part of a plant that falls off in autumn.

Leaf

100

Plural form of an item filled with pages and used for reading.

Books

100

These farm animals have the same form in both singular and plural.

Sheep

200

Singular noun of a small domesticated feline often kept as a pet.

Cat 

200

Plural form of a large urban area.

Cities

200

Singular form of a bird known for its honking sound.

Goose

200

Plural form of a common fruit that's often red or green.

Apples

200

This word for an aquatic animal remains the same whether singular or plural.

Fish 

300

Singular noun of a vehicle with four wheels used for transportation.

Car

300

Plural form of an adult female

Women

300

Singular form of young people

Child

300

Plural form of a yellow tropical fruit often found in bunches

Bananas

300

This article of clothing has the same name in singular and plural forms

Pants

400

Singular noun for a building where people live.

House

400

Plural form of a small rodent often found in houses.

Mice

400

Singular form of adult males.

Man

400

Plural form of a piece of furniture used for sitting.

Chairs 

400

Plural form of a microscopic organism often found in colonies.

Bacteria 

500

Singular noun for a tall plant with leaves and branches.

Tree

500

Plural form of a part of the body used for walking.

Feet

500

Singular form of the hard structures in the mouth used for chewing.

Tooth

500

Plural form of a writing instrument filled with ink.

Pens

500

Plural form of an unusual event or occurrence.

Phenomena