I believe the answer to your question is B.
A line that marks the outer limmits of an object or figure
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, <em>B</em> and <em>D</em> are the answers to our question.
Answer:
I believe the answer is D. I don't know if a second answer is needed.
1. do you walk, I'm not going, is raining
2. is Boris doing, is watching
3. do your parents work, visit, have
4. is looking, do you know, doesn't sleep
5. am waiting, do you know, is studying
6. do you want, I'm looking after