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: Which of the following is greatest?

Option A: 1/10

Option B: 1/100

Option C: 1/1000

Option D: 1/10^9

Option E: 1/5
Option E

Question: During a certain week, a seal ate 60% of the first 80 smelt it came across, and 30% of the remaining smelt it came across. If the seal ate 40% of the smelt it came across during the entire week, how many smelt did it eat?

Option A: 32

Option B: 40

Option C: 96

Option D: 64

Option E: 80
Option C

Question: If (A-B-C+D = 13) and (A+B-C-D = 3), what is the value of (B-D)^2?

Option A: 4.

Option B: 8.

Option C: 12.

Option D: 25.

Option E: 64.
Option D