The answer to your question would be 'A'
Answer:

Step-by-step explanation:
From C-A, it goes from y=1 to y=5, so that 4 units
From A-B, it goes from x = -1 to x = 4, that is 5 units
Now, to find distance from B to C, we need to use the distance formula:

Where the variables are the respective points of B and C,
B (4,5) & C(-1,1)
So x_1 =4, y_1=5, x_2=-1, y_2=1
Plugging into the formula we get:

Summing it all (perimeter is sum of 3 sides):
Distance = 
3rd answer choice is right.
Answer:
The principal square root of -4 is 2i.
Step-by-step explanation:
= 2i
We have the following steps to get the answer:
Applying radical rule 
We get 
As per imaginary rule we know that 
= 
Now 
Hence, the answer is 2i.