Penguins (a)   during the cold Antarctic winter. (sinh sản)

Birds usually (a)   with one partner during the breeding season. (giao phối)

The eggs will (a)   after about three weeks. (nở trứng)

The penguins (a)   together to stay warm. (tụ lại, quây quần)

A (a)   of ants built a large nest underground. (đàn, bầy)

The rainforest is a rich (a)   full of life. (hệ sinh thái)

There is a strong (a)   between plants and animals in nature. (sự liên kết)

A lion’s (a)   mainly consists of meat. (chế độ ăn)

Plants are (a)   because they make their own food. (sinh vật sản xuất)

Rabbits are (a)   that eat plants. (sinh vật tiêu thụ bậc 1)

Snakes are (a)   that eat small animals like frogs. (sinh vật tiêu thụ bậc 2)

Eagles are (a)   at the top of the food chain. (sinh vật tiêu thụ bậc 3)

The caterpillar eats the (a)   of plants. (lá)

Mammals are covered in (a)   to keep warm. (lông, tóc)

The frog’s tongue is (a)   to catch insects. (dính)

Water is the most common (a)   on Earth. (chất lỏng)

The Venus flytrap can (a)   insects inside its leaves. (bẫy)

The crab uses its claws to (a)   shells. (nghiền, ép)

The plant releases (a)   to digest its prey. (dịch, nước)

Sugar can easily (a)   in hot water. (hòa tan)

Humans (a)   food using enzymes in the stomach. (tiêu hóa)

The teacher showed (a)   of the human body. (sơ đồ, biểu đồ)

Scientists took (a)   of the new bird species. (ảnh chụp)

The class used a (a)   of the solar system. (mô hình 3D)

Students observed (a)   such as rocks and shells. (vật thật)

We watched (a)   about ocean life in class. (video)

Fish, birds, and mammals are all (a)   . (động vật có xương sống)

Dolphins must come to the surface to (a)   . (thở)

Polar bears have thick (a)   to keep them warm. (lông mượt)

Fish use (a)   to breathe underwater. (mang)

Humans and whales both use (a)   to breathe air. (phổi)

Reptiles are covered in (a)   for protection. (vảy)

Frogs can absorb water through their (a)   . (da)

The fish moves quickly using its (a)   . (vây)

The turtle hides inside its (a)   when frightened. (vỏ cứng)

Birds use their (a)   to fly and stay warm. (lông vũ)

A snake lays its (a)   in the sand. (trứng)

A (a)   of dolphins swam past the boat. (một đàn cá heo)

Whales eat tiny (a)   in the ocean. (sinh vật phù du)

A mule is a (a)   between a horse and a donkey. (con lai)

Dolphins use sound at different (a)   to communicate. (tần số)

Sound is measured in (a)   . (đơn vị đo tần số)

The ship used (a)   to detect submarines. (thiết bị định vị âm thanh dưới nước)

(a)   study life forms that live in the ocean. (nhà sinh vật biển)

The Pacific (a)   is the largest in the world. (đại dương)

The animals were rescued and moved to a wildlife (a)   . (khu bảo tồn)

Scientists used a (a)   to follow the whale’s movements. (thiết bị theo dõi)

Birds travel long distances during (a)   . (sự di cư)

Tigers are an endangered (a)   . (loài)

Researchers placed underwater (a)   to record whale sounds. (micro thu âm)

A (a)   elephants was drinking by the river. (một đàn voi)

The cat gave birth to (a)   kittens. (một lứa mèo con)

A (a)   wolves hunted together in the forest. (một bầy sói)

A (a)   birds flew across the sky. (một đàn chim)

A (a)   lions rested in the sun. (một bầy sư tử)

Coral reefs are the natural (a)   of many fish. (môi trường sống)

We saw (a)   elephants drinking water by the river. (một đàn voi)

A (a)   birds flew across the blue sky. (một đàn chim)

The (a)   lions rested under the tree after hunting. (một bầy sư tử)

A (a)   wolves surrounded the deer in the forest. (một bầy sói)

Our dog gave birth to (a)   puppies last night. (một lứa chó con)

A (a)   dolphins followed the ship playfully. (một đàn cá heo)

We saw (a)   fish swimming together in the ocean. (một đàn cá)

A (a)   bees gathered around the flowers. (một đàn ong)

The scientist found (a)   ants living under the tree. (một đàn kiến)

We saw (a)   monkeys jumping from tree to tree. (một bầy khỉ)

Our school has (a)   players competing in the football match. (một đội bóng)

A (a)   people gathered to watch the fireworks. (một đám đông người)

She gave me (a)   beautiful roses for my birthday. (một bó hoa)

He handed her (a)   red tulips with a smile. (một bó hoa)

There was (a)   books on the teacher’s desk. (một chồng sách)

My mother bought me (a)   new paintbrushes. (một bộ cọ vẽ)

The children made (a)   leaves in the garden. (một đống lá)

He’s wearing (a)   new shoes today. (một đôi giày)

A (a)   tourists visited the museum this morning. (một nhóm khách du lịch)

The police arrested (a)   thieves last night. (một băng trộm)

The teacher smiled at (a)   eager students. (một lớp học sinh)

A (a)   ships sailed out to sea at dawn. (một hạm đội tàu)

An (a)   soldiers marched through the valley. (một đạo quân)

She wore (a)   pearls around her neck. (một chuỗi ngọc trai)

The shop sells (a)   high-quality clothes. (nhiều loại, một loạt)

The writer published (a)   books about wild animals. (một loạt sách)

He has (a)   stamps from all over the world. (một bộ sưu tập tem)

A (a)   experts discussed the new environmental law. (một nhóm chuyên gia)

The captain gave orders to (a)   sailors on the ship. (một thủy thủ đoàn)

The church was filled with the voices of (a)   singers. (một dàn hợp xướng)

The concert began with (a)   musicians playing drums and guitars. (một ban nhạc)

He hung (a)   bananas on the kitchen hook. (một nải chuối)

The event was attended by (a)   famous movie stars. (một dàn sao)

A (a)   swans floated gracefully on the lake. (một đàn thiên nga)

The museum displayed (a)   ancient artifacts. (một loạt, vô số hiện vật)