Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.

By the end of the 21st century, scientists _______ a cure for the common cold.

A. will find

B. will have found

C. will be finding

D. will have been finding

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.

By the end of the 21st century, scientists _______ a cure for the common cold.

A. will find

B. will have found

C. will be finding

D. will have been finding

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each unfinished sentence.

By the end of the 21st century, scientists _______ a cure for the common cold

A. will find

B. will have found

C. will be finding 

D. will have been finding

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

By the end of the 21st century, scientists__________a cure for the common cold

A. will find 

B. will have found 

C. will be finding 

D. will have been finding

Mark the letter A, B, Cor D on your answer sheet to indicate the correct answer to each of the following questions

According to some optimistists, by the end of the 21st century, our astronauts ______ on Mars.

A. will be landing 

B. have landed 

C. will land 

D. will have landed

Mark the letter A, B, c, or D on your answer sheet to indicate the correct answer to each of the following questions.
So far there is no vaccine________in sight for the common cold.

A. or curing

B. having cured

C.has cured

D.or cure

Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

A cure for the common cold, causing by a virus, has not been found

A. for

B. causing

C. a virus

D. has not been found

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
Many natural resources_________by 1he end of the century.

A. had disappeared

B. have disappeared

C. disappeared

D. will have disappeared