Answer:
2) In particular
Step-by-step explanation:
The first sentence talks about how Clara Barton was actually a pioneer in more ways than just her involvement in the American Red Cross. The second sentence goes on to talk about a specific example about how she was a pioneer in other ways.
"Nevertheless" lends a sense of contrast; however, here the second sentence is merely reinforcing the first, so it's not "nevertheless".
"In particular" is synonymous to the phrase "for example" or "for instance", both of which fit here. So that's the answer.