11.  And by every measure, the problem is a complex one.

12.  But in total, Russian surgeons perform far fewer bypass operations, particularly the complex ones, than do surgeons in many other countries.

13.  But if the old racial order has eroded, a more complex one has replaced it.

14.  But if the old racial order, of whites always on top, has eroded, a more complex one has replaced it.

15.  But more complex ones with minute parts can break during cleaning, which manufacturers and physicians worry about.

16.  But the political calculus is a complex one.

17.  He particularly likes how the writers have humanized Tony and turned what could have been a one-dimensional character into a complex one.

18.  Her story was a complex one that never seemed to end.

19.  Her character in the film, Grace, is a very complex one.

20.  His question is a complex one.