I think its a
because the line segments connect each other.
To convert any unit to it's "milli-" form always multiply the given value by 1000. The new value will be the value of in the "milli-" form.
The question asked to us is to convert 3.521 g to mg (or milligram). Thus, all that we need to do is to multiply 3.521 with 1000 and we will get the corresponding value in milligrams. Thus, in mg, 3.521 g is:
mg
Option B. 12/ 125 is the answer.
Explanation
Total umber of sour ball candies = 50
Number of lemon candies = 12
Hence the probability to get a lemon candy is = 12/50
Number of cherry sour balls = 20
So, the probability to get a cherry sour ball = 20/50
So, to get the joint probability for a random selection to either get a lemon or cherry candy, we will multiply both the probabilities.

= 
this isn’t an answer but uhm, why are you doing 5th grade equations in HIGH SCHOOL