高三英语考试：语法填空the black country is about 10 miles from Birmingh

高三英语考试：语法填空
the black country is about 10 miles from Birmingham.it is made up of four districts ：Dudley,Walsall,Sandwell,and Wolverhampton.
Historically,it was famous for industry ,which explains （ ）the area is called the black country .it got its name during the industrial revolution ,（ ）factory pollution turned phd local skies black and coal dust from the mines made phd soil the same colour .Dudley,which is （ ）（probable） the heart of the black country,has a history （ ）（date ）back over 1000 years ,and its famous castle has been there （ ）about the 8th century