this one must have been in the possesion of a private collector请问这个句子成分怎么划分?特别是have been 这块!

I found this book when Icame to the classroom.It must must have been left by one the students this one must have been in the possession of a private collector 为什么用have,第三人称不是用has吗this one must have been in the possession of a private collector 为什么用have,第三人称不是用has吗 A,Excuse me .( ) B,Sorry,I don't have one A,So I must go to the shop near our school .A:Excuse me .( ) B:Sorry,I don't have one A:So I must go to the shop near our school .B:I think the shop is closed at this time of day .A:( ) B:It's friday .On frid Must l hard in this paper one hoMust l hard in this paper one hour later Yes,you——A need B must C may D will I must finish this work_____________(one). have与has的区别this one must have been in the possession of privite collectorthis one 不是第三人称么不是应该用has么 两个英语问题(请附详细解析_________happened to be no one in the room when the fire broke out.A．It B.This C.There D.That—Oh,the meat has gone bad!—You ________ it in the refrigerator.A.must not have kept B.must have kept C.should have I have this one here. My bike is broken.I____buy one.A.could B.need C.have to D.must We must have this work______before 10:00.A finish B finished C to finish D finishing this one must have been in the possesion of a private collector请问这个句子成分怎么划分?特别是have been 这块! ----Wsa that the new school master who walked by?----_______A.It must be that B.It must have been C.He must be D.This must have been为什么选B啊 6.---Was that new school master who walked by --- _____.A.It must be that B.It must have beenC.He must be D.This must have been请问这个题为什么选B since this road is wet and slippery this morning,it----last night.a.must rain b.was rainingc.must have rained d.may rain Somebody here only this morning A must be B can be C must have been D should have beensomebody 和here 中间空 Mary ___on her new priject late last night ,so she felt sleeply in the office this morninga.must work b.must have been working c.must be working d.must have been worked选什么. Since the road is wet this morning,---------last night.A it must rain B it must have rainde C it must be raining D it must have been raining 选什么 为什么 Since the road is wet this morning,---------last night.A it must rain B it must have rainde C it must be raining D it must have been raining