All the students _______ very hard over the last three years.
A:works
B:has worked
C:have worked
D:worked
已知 x2−2=0 ,求代数式 (x−1)2x2−1+x2x+1 的值.
—What are you going to do after the exams to Senior High School?
—I am going to _____________ for vacation.
适合作为如图名称的是( )