our pastry is of prime quality.为什么要加个介词of 去掉可以吗?

our pastry is of prime quality.为什么要加个介词of 去掉可以吗? This is our witness of pastry chef PASTRY怎么样 pastry是什么意思 Open a can ______(on,of)tomatoes sauce and spread it______(on,of)the pastry. Mr Zhang is the ( )of our school Clover is the witness of our This is not our range of It is getting way our of This is the_______ (begin) of our tour. our country is short of energy Smoke is clouding our view of global Shanghai is()the east of our country passion is the source of our happiness it is our final source of power it is of our ciassroom的意思 Who is the ruler of our courntry?