Answer:
20 +2√10 units
Step-by-step explanation:
The length BC is given by the difference of the x-coordinates on that horizontal line:
BC = 5 -(-5) = 10
The perimeter is the sum of the side lengths, so is ...
P = AB +BC +AC = 10 + 10 + 2√20
P = 20 +2√20 . . . . . matches the last choice
