Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.
Today, many serious childhood diseases ______ by early immunization.
A.can be prevented
B.can prevent
C.prevent
D.are preventing

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
There ____ a number of reasons for the falloff the Roman Empire.
A.are said being
B.was said being
C.said to be
D.are said to have been

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Gordon wants to look his best at the wedding so he’s __________.
A.having a suit made
B.having made a suit
C.to get made a suit
D.make a suit

Choose the best answer to complete the following question.
Ted ______ by a bee while he was sitting in the garden.
A.got stung
B.gets stung
C.get stung
D.got sting

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Her boyfriend is said _________ in the army two years ago.
A.have served
B.to have served
C.to serve
D.serving

Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
______ broken several world records in swimming.
A.It is said to have
B.She is said to have
C.People say she had
D.She is said that she has

Đa thức $ M $ nào dưới đây thỏa mãn tổng của M và đa thức: $ {{x}^{3}}+3{{x}^{2}}y-5x{{y}^{2}}-7xy-2 $ là một đa thức bậc 0.
A. $ M=-{{x}^{3}}-3{{x}^{2}}y+5x{{y}^{2}}+7xy. $
B. $ M=-{{x}^{3}}-3{{x}^{2}}y+5x{{y}^{2}}-7xy. $
C. $ M=-{{x}^{3}}-3{{x}^{2}}y-5x{{y}^{2}}+7xy. $
D. $ M=-{{x}^{3}}+3{{x}^{2}}y+5x{{y}^{2}}+7xy. $

Rút gọn biểu thức $ \left( 6,7x{{y}^{2}}-2,7xy+5{{y}^{2}} \right)-\left( 1,3xy-3,3x{{y}^{2}}+5{{y}^{2}} \right)$ ta được
A. $ -10x{{y}^{2}}-4xy. $
B. $ 10x{{y}^{2}}+4xy. $
C. $ 10x{{y}^{2}}-4xy. $
D. $ -10x{{y}^{2}}+4xy. $

Cho hai đa thức $ M={{x}^{2}}-2xy+{{y}^{2}} $ và $ N=4{{x}^{2}}-{{y}^{2}}-xy+1 $ . Kết quả của $ M-~N $ là
A. $ -3{{x}^{2}}-xy+2{{y}^{2}}-1 $ .
B. $ 3{{x}^{2}}-xy+\dfrac{5{{y}^{2}}}{3}-1 $ .
C. $ -3{{x}^{2}}-xy+2{{y}^{2}} $ .
D. $ -3{{x}^{2}}-xy+{{y}^{2}}-1 $ .

Rút gọn biểu thức $ \left( {{x}^{2}}+{{y}^{2}}-2xy \right)-\left( {{x}^{2}}+{{y}^{2}}+2xy \right)+\left( 4xy-1 \right)$, ta được
A. $ 2{{x}^{2}}+2{{y}^{2}}+8xy+1. $
B. $ -1. $
C.0.
D.1.