have been made是什么時態

　　Errors may have been made due to human fallibility.

　　這些過失可能是人為犯錯造成的。

　　A number of simplifications have been made to the taxation system.

　　稅收制度已經歷過多次簡化。

　　Check that all windows and doors have been made as secure as possible.

　　看看是不是所有的門窗都關緊了。