This means "what benefits does the volcanic activity have for the population?" I would say that the main benefit of continental volcanic activity is the expulsion of ash which can enrich the soil and in the tropics make it good for growing coffee, for example, as it does in El Salvador.
A would be the right choice i think not really enough information.
1st, let's calculate the side AB = c in applying the law of cosine:
AC² = BC²+AC² - 2AB.BC. cos87°)
c²= 10.1²+9.8²-2(10.1)(9.8)(cos(87)
c²=102.01 + 96.04 -196.96cos(87)
c² = 187.74 and c = 13.7
Having calculated the 3rd side, now we can apply Heron's formula for the area:
AREA = √p(p-a)(p-b)(p-c), where p is half the perimeter or p=(a+b+c)/2 =16.8
AREA = √16.8(16.8-10.1)(16.8-9.8)(16.8-13.7)
AREA = 49.42 OR 49.4 unit²
