Câu hỏi: The developing of the submarine was hindered by the lack of a power source that could propel an underwater vessel.

A. developing

B. the

C. a power

D. could propel

Câu 1: Doctors believe there is better in this modern world of ours to try to prevent illnesses than to rely on medicines to cure them.

A. doctors

B. there is

C. of ours

D. to

Câu 2: A beaver uses its strong front_teeth to cut down trees and peel_off its bark.

A. its

B. front teeth

C. eel off

D. its

Câu 3: The Red Cross organizes and leads relief assistance missions after natural disasters such as floods, tsunamis, earthquakes, and homelessness.

A. The Red Cross

B. organizes and leads

C. assistance missions

D. and homelessness

Câu 4: Species like snakes, lizards, coyotes, squirrels, and jack rabbits seems to exist quite happily in the desert.

A. like

B. seems to

C. quite happily

D. the

Câu 5: These snakes will not cause you any serious harm. They are harmful.

A. snakes

B. cause

C. harm

D. harmful

Câu 6: By the turn of the century, most of the inventions that were to bring in all the comforts of modern living has already been thought of.

A. By the turn of

B. that

C. were to

D. has already been