The research mainly deals with the difficulty the students have ______ their attention pm their study all the time.
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A
to focus
B
to be focused
C
focusing
D
focused
推荐题目
 –Why has Tom looked unhappy recently? –He has some difficulty ______ with his new classmates at school.
#64476
A
getting over  
B
getting in   
C
getting along
D
getting down
Do you know how much time and effort they devoted___________such a complicated project ? 
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A
to complete
B
completed
C
completing
D
to completing