Jack ()so strong. He can lift the heavy boxes
A. was
B. is
C. be
D. will be
釉质的哪一层抗龋能力最强
A. 表层0.1~0.2mm B.表层0.2mm以内
B. 中层
C. 内层
D. 各层抗龋能力一致
Kathy ()to South Korea more than five times
A. have been
B. has went
C. gone
D. has been
Our students are free to study () interests them.
A. that
B. which
C. whatever
D. anything