The answer for Part A is B. lead as a guide, as we can get clues from the keywords "ranger", which means a person who protects the natural park or a forest, and is likely to be a guide. "teach" and "shows visitors around " are the duty of a guide which also indicates her role as a guide.
From the above we can also conclude that the answer for Part is C."shows visitors around " because this is the clearest keywords showing her role as a guide.
Therefore the answer Part A is B and Part B is C.
Hope it helps!
