The two sentences included in the excerpt that demonstrates that Shackleton felt his men displayed determination in difficult situations are the following observations :
"When we were all chilled almost to the limit of endurance, did we manage to get the stove alight and make ourselves hot drinks (The carpenter was suffering particularly, but he showed grit and spirit)"
"The slope we were traversing appeared to end in a precipice above this beach. (But our revived spirits were not to be damped by difficulties on the last stage of the journey, and we camped cheerfully for breakfast)"
Then, B and D are the answers to our question.