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.

Q: Question: The greatest common factor of 16 and the positive integer n is 4, and the greatest common factor of n and 45 is 3. Which of the following could be the greatest common factor of n and 210?

 Option A: 3

 Option B: 14

 Option C: 30

 Option D: 42

 Option E: 70

A: Option D
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Q: Question: Triangle STV has sides ST = TV = 26, and SV = 20. What is the area?

 Option A: 160

 Option B: 180

 Option C: 200

 Option D: 220

 Option E: 240

A: Option E
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Q: Question: Using all the letters of the word "HEAD", how many words can be formed, which begin with H and end with D?

 Option A: 8

 Option B: 4

 Option C: 2

 Option D: 7

 Option E: 9

A:
Option C
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