Choose the best answer for the following sentence:
 No one seemed to notice my ____________ and I felt so lonely.
A. message
B. friendliness 
C. existence
D. living

Choose the best answer for the following sentence:
There are several ___________ to attract the attention of other people.
A. chooses
B. chose
C. chosen
D. choices

Choose the best answer for the following sentence:
Be quiet, please. We ______________ at the translation and you _________________ a lotof noise. 
A. are working - are making            
B. work - are making 
C. are working - make       
D. work - make

Choose the best answer for the following sentence:
I am reading this novel. By the time you come back from work I _____________________ .
A. shall finish         
B. will finish 
C. shall have finished                  
D. have finished

Choose the best answer for the following sentence:
She __________________ of great help to us since she ________________ for such a long timewith us.
A. has been - has lived         
B. has been - has been living
C.  has been - lived            
D. A and B are correct

Choose the best answer for the following sentence:
Books are a wonderful source _____________ knowledge and pleasure. 
A. with                       
B. of                     
C. in                     
D. about

Cho phương trình: $\displaystyle \left( {{m}^{2}}+2 \right){{\cos }^{2}}x-2m\sin 2x+1=0$. Để phương trình có nghiệm thì giá trị thích hợp của tham số là 
A. $\displaystyle -1\le m\le 1$ 
B. $\displaystyle -\frac{1}{2}\le m\le \frac{1}{2}$ 
C. $\displaystyle -\frac{1}{4}\le m\le \frac{1}{4}$ 
D. $\displaystyle |m|\ge 1$

Phương trình $\frac{\sqrt{2}\sin x-1}{\cot 2x}=0$ có nghiệm là
A. $x=\frac{3\pi }{4}+k\pi ,k\in Z.$
B. $\left[ \begin{array}{l}x=\frac{3\pi }{4}+k\pi \\x=\frac{\pi }{4}+k\pi \end{array} \right.,k\in Z.$
C. $x=\frac{\pi }{6}+k\pi ,k\in Z.$
D. Một kết quả khác.

Phương trình $\sin x+\cos x=1-\frac{1}{2}\sin 2x$ có nghiệm là
A. $\left[ \begin{array}{l}x=\frac{\pi }{6}+k2\pi \\x=k\pi \end{array} \right..$
B. $\left[ \begin{array}{l}x=\frac{\pi }{2}+k2\pi \\x=k2\pi \end{array} \right..$
C. $\left[ \begin{array}{l}x=\frac{\pi }{8}+k\pi \\x=k\frac{\pi }{2}\end{array} \right..$
D. $\left[ \begin{array}{l}x=\frac{\pi }{4}+k\pi \\x=k\pi \end{array} \right..$

Cho hàm số $y=\frac{{{\cos }^{3}}x+1}{{{\sin }^{3}}x}.$ Tập xác định của hàm số là
A. $R\backslash \left\{ k\pi |k\in Z \right\}.$
B. $R\backslash \left\{ \frac{\pi }{2}+k\pi |k\in Z \right\}.$
C. A và B đúng.
D. $R\backslash \left\{ \pi +k\pi |k\in Z \right\}.$