Answer: D. Rural electrification administration
Explanation:The Rural Electrification Act of 1936 provided federal loans for the installation of electrical distribution systems for rural areas of the US
The use of submarines in modern warfare helps to store nuclear warheads which can be prepared at a moment's notice to strike a target.
<h3>What is Modern Warfare?</h3>
This refers to the use of modern methods and means to be able to preserve their battle worthiness.
Also, a submarine can carry a large crew and equipment and remain submerged underwater for about 6 months, patrolling, collecting underwater information, spy operations, and defense mechanisms.
Please note that your question is incomplete so I gave you a general overview to help you get a better understanding of the concept.
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Sextant, Astrolabe, Chip log, nautical charts, mariner's compass, chronometer, etc