What is the square root of -1?
a. -i
b. i
c. -1
d. 1

It is the option B that is 'i'.

B. i

Step-by-step explanation:

Given :

The square root of -1 written as

When there is a negative number in the square root it is called as an imaginary number.

And imaginary number is denoted by 'i'

and the value for i is

for an example

Hence the answer is 'i'.

x= cost per bracelet

number of bracelets * x + shipping charge = total cost

so

9x+9=72