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.

Question: A shirt goes on sale for 80% of its original price. One week later, the sale price is marked down 20%. The final price is what percent of the original price?

 Option A: 72%

 Option B: 70%

 Option C: 52%

 Option D: 64%

 Option E: 28%
Option D

Question: A and B complete a work in 6 days. A can alone can do it in 10 days. If both can together can do the work in how many days?

 Option A: 7

 Option B: 3.75

 Option C: 2

 Option D: 1

 Option E: 8
Option B

Question: Two trains of equal are running on parallel lines in the same direction at 45 km/hr and 36 km/hr. The faster train passes the slower train in 36 sec. The length of each train is?

 Option A: 45

 Option B: 88

 Option C: 66

 Option D: 55

 Option E: 22

Option A