You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

[EX Q]: Question: The average marks of a class of 35 students is 45 and that of another class of 55 students is 65. Find the average marks of all the students?

 Option A: 52.6

 Option B: 52.4

 Option C: 52.1

 Option D: 57

 Option E: 52.9
[EX A]: Option D

[EX Q]: Question: The probability that a visitor at the mall buys a pack of candy is 30%. If three visitors come to the mall today, what is the probability that exactly two will buy a pack of candy?

 Option A: 343

 Option B: 147

 Option C: 189

 Option D: 063

 Option E: 027
[EX A]: Option C

[EX Q]: Question: There are 10 students named alphabetically from A to J. What is the Probability that A and D do not sit together if all 10 sit around a circular table?

 Option A: 2/9

 Option B: 2/5

 Option C: 7/9

 Option D: 4/5

 Option E: 8/9
[EX A]:
Option C