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: How much time will it take for an amount of Rs. 900 to yield Rs. 81 as interest at 4.5% per annum of simple interest?

 Option A: 2 years

 Option B: 3 years

 Option C: 1 year

 Option D: 4 years

 Option E: 5 years
Option A

Question: The greatest number that divides 180, 565 and 705 leaving remainder 5, 5 and 5 respectively is:

 Option A: 31

 Option B: 33

 Option C: 35

 Option D: 38

 Option E: 39
Option C

Question: A boat crossed a lake from East to West at the speed of 5 km/h, entered a river and covered twice as much distance going upstream at 4 km/h. It then turned around and stopped at the south shore of the lake. If it averaged 3.6 km/h that day, what was its approximate downstream speed?

 Option A: 4

 Option B: 5

 Option C: 6

 Option D: 7

 Option E: 8

Option C