几道英语单选 请注明原因和答案,谢
1,Although the universe seems enormous,I think it has a(n) ____.
A.orbit B.limit C.destination D.length
2.We are best friends,but we ____ each other for about ten fears since graduation.
A.didn't see B.haven't seen C.hadn't seen
3.By the year 2020,I may have had ____ robot shaped like____ human in the house to help me with the housework.
A./;the B.a;the C.the;a D.a;a
4.____ himself well in public is his goal,but he hasn't quite mastered it yet.
A.To express B.Having expressed C.Express D.Expressed