Để đánh giá loại liên kết trong phân tử hợp chất, người ta có thể dựa vào hiệu độ âm điện. Khi hiệu độ âm điện của hai nguyên tử tham gia liên kết nhỏ hơn 0,4 thì đó là liên kết
A.cộng hoá trị có cực.
B.kim loại.
C.cộng hoá trị không cực.
D.ion.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Darwin’s theory of __________has helped to explain the disappearance of some species and the survival of others.
A.innovation
B.development
C.evolution
D.improvement

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Dinosaurs and mammoths are classified as EX, meaning extinct, on the _________ status scale.
A.conservation
B.conversation
C.protection
D.preservation

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Programs to raise public _____ about protecting wild and endangered animals have been conducted.
A.recognition
B.care
C.attention
D.awareness

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Climate scientists have measured the temperature and________on every part of the Earth over many years.
A.rain level
B.rainfall
C.fall in rain
D.level of rain

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Many people think the money spent on protecting ___________ species should be used for improving the lives of the local residents.
A.endanger
B.dangerous
C.danger
D.endangered

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
I don’t have chance to see a lot of ______animals because I live in a big city.
A.wildlife
B.species
C.mammals
D.insects

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Many nations have laws offering protection to these species, such as forbidding hunting, restricting land development or creating _______.
 
A.agencies
B.challenges
C.awareness
D.reserves

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
The river around my village used to have the greastest__________ of freshwater fish in the country, but now very few species are found here.
A.diversified
B.various
C.diversity
D.variousness

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Living in warm waters, sea turtles_______hundreds of miles between their feeding grounds and the beaches where they nest and lay eggs.
A.migrate
B.swimming
C.migrating
D.swim