People usually (1- sing)_______________ because they like music or because they feel happy. They express their happiness by (2-sing)______________ . When a bird sings,however its song usually (3- mean)...

People usually (1) sing because they like music or because they feel happy. They express themselves

by (2) singing. When a bird sings, however, its song usually (3) means more than that the bird

(4) is happy. Birds (5) have many reasons for singing.

They sing to (6) give information. Their songs are their language. The most beautiful songs

(7) are sung by male (cock) birds. They sing when they want to (8) attract a female (hen) bird.

It is their way of (9) saying that they are looking for a wife. Birds also sing to tell others to

(10) keep away. To a bird, his tree or even a branch of a tree is his home. He does not want others near

him, so he sings to warn them.

$$ Answer:

sing (hiện tại đơn)

singing (danh động từ)

means (hiện tại đơn, ngôi thứ 3 số ít)

is (động từ "to be" ở hiện tại)

have

give (nguyên thể sau "to")

are (bị động – "are sung")

attract (nguyên thể sau "want to")

saying (danh động từ)

keep (nguyên thể sau "to tell sb to...")