Sentence Correction

Having established a base camp in McMurdo Sound and spent the winter of 1908 there, Ernest Shackleton headed south with three men, four ponies and supplies, but because of conditions in the Antarctic inland so brutal that all of the ponies died, his party ultimately failed to reach the South Pole, turning around at a then-record of a latitude of 88°23' South.

A) because of conditions in the Antarctic inland so brutal that all of the ponies died, his party ultimately failed to reach the South Pole, turning around

B) because of conditions in the Antarctic inland of such brutality so that all of the ponies died, his party failing ultimately to reach the South Pole, to turn around

C) because conditions in the Antarctic inland being as brutal as to kill all of the ponies, his party failing to reach ultimately the South Pole, turning around

D) because conditions in the Antarctic inland had been this brutal so that all of the ponies died, his party ultimately failed to reach the South Pole, turned around

E) because conditions in the Antarctic inland are so brutal as to kill all of the ponies, his party failing to reach ultimately the South Pole, turning around

The OA is A.

I thought the right option was B. What is wrong with it?