甲完成乙委托设计的厂徽，但双方并未约定其著作权的归属。因此该厂徽的著作权应当归属于（）
A、乙
B、乙的主管机关
C、甲
D、甲与乙
参考答案：C
He must be helping the old man to water the flowers, _____?[ ]
A. is he
B. isn't he
C. must he
D. mustn't he
The lighthouse if（）at night may be in trouble.
A.invisible
B.it is invisible
C.isn't visible
D.unvisible
