11.   Cutting down vast areas of the rainforests has created serious ecological problems.

12.   Even a cursory examination of the documents would reveal some serious problems.

13.   Even if returns improve, the pension system still faces serious problems.

14.   Evidence strongly suggests that a serious problem exists and research is needed to better understand this phenomenon and its causes.

15.   Fire officials said bee stings and poison oak were the most serious problems.

16.   Guaranteeing continuity in the casework of clients is a serious problem for a manager with a large team of volunteers.

17.   However, there are still serious problems.

18.   I think this is a very convenient sort of way to detract attention from much more serious problems.

19.   I want a forum to address the most serious problem facing the people of this state.