In this task, You are given an open-domain question that can be answered based on factual information. Your task is to provide \*short\* answer (in a few words only) for the given question. The short answer can be one or more entities or it can also be boolean \*yes\* or \*no\*.
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Question: who is the principal assistant to the president in all matters relating to the dod

Answer: Secretary of Defense


Question: who is the longest serving director of isro

Answer: Dhawan, Satish


Question: when did the transcontinental railroad started being built

Answer:
1863