英文文法結構

When someone rings-----S+V
the police----------object
after discovering their TV set has been stolen-----s+v--as Subordinate clause
------There is little point------S+V----as Main clause
in terms of---------phrase
identifying---------verbal phrase
those responsible for the crime---------co-ordinate phrase of reason
in ensuring --------verbal
a very rapid response------co-ordinate phrase of reason again,
(from members of family.)-----object of co-ordinate phrase

Briefly it means:-Main clause+Subordinate clause;
eg:-You don't know the crime.