Answer
Option C is obviously the answer.
Explanation
It will be easy to answer this by providing the answers to the expressions.
Option A
18.8 - 6.5 = 12.3 (3 significant figures)
Option B
4350 - 2210 = 2140 (4 significant figures)
Option C
15.4 - 8.1 = 7.3 (2 significant figures)
Option D
54.5 * 30.7 = 1673.15 (6 significant figures)
Hope this Helps!!!