A.
The problem itself isn't new.
B.
Experts finally traced the cause of her illness.
C.
Problems began as soon as the couple moved in, however.
D.
They spent a lot of money on decorating the house.
E.
Because of such leaks, the air in an average home was replaced by fresh outdoor about once an hour.
F.
It was as tough she had suddenly developed a strange illness. (46)