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 man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is:

 Option A: 2 km/hr

 Option B: 1 km/hr

 Option C: 4 km/hr

 Option D: 6 km/hr

 Option E: 5 km/hr
Option B

Question: 10 3/4 + 7 2/17 - 9 1/15=?

 Option A: 7 719/1020

 Option B: 9 817/1020

 Option C: 9 719/1020

 Option D: 8 817/1020

 Option E: None of them
Option D

Question: Robet traveled a distance of 30 km, covering the first 10 km in x minutes, the next 10 km in y minutes and the last 10 km in z minutes. If he totally took 3y minutes to cover the whole distance, then which of the following cannot be true? Assume x , y and z are different.

 Option A: z=3x

 Option B: x=3z

 Option C: y=2x

 Option D: x=2y

 Option E: y=3x

Option D