Read the text below to answer questions 16-20.
Background
The Naval Nuclear Propulsion Program (NNPP) started in
1948. Since that time, the NNPP has provided safe and effective
propulsion systems to power submarines, surface combatants,
and aircraft carriers. Today, nuclear propulsion enables virtually
undetectable US Navy submarines, including the sea-based leg
of the strategic triad, and provides essentially inexhaustible
propulsion power independent of forward logistical support to
both our submarines and aircraft carriers. Over forty percent of
the Navy's major combatant ships are nuclear-powered, and
because of their demonstrated safety and reliability, these ships
have access to seaports throughout the world. The NNPP has
consistently sought the best way to affordably meet Navy
requirements by evaluating, developing, and delivering a variety
of reactor types, fuel systems, and structural materials. The
Program has investigated many different fuel systems and
reactor design features, and has designed, built, and operated
over thirty different reactor designs in over twenty plant types to
employ the most promising of these developments in practical
applications. Improvements in naval reactor design have allowed
increased power and energy to keep pace with the operational
requirements of the modern nuclear fleet, while maintaining a
conservative design approach that ensures reliability and safety
to the crew, the public, and the environment. As just one
example of the progress that has been made, the earliest
reactor core designs in the NAUTILUS required refueling after
about two years while modern reactor cores can last the life of a
submarine, or over thirty years without refueling. These
improvements have been the result of prudent, conservative
engineering, backed by analysis, testing, and prototyping. The
NNPP was also a pioneer in developing basic technologies and
transferring technology to the civilian nuclear electric power
industry. For example, the Program demonstrated the feasibility
of commercial nuclear power generation in this country by
designing, constructing and operating the Shipping port Atomic
Power Station in Pennsylvania and showing the feasibility of a
thorium-based breeder reactor.
In: Report on Low Enriched Uranium for Naval Reactor Cores. Page 1.
Report to Congress, January 2014.
Office of Naval Reactors. US Dept. of Energy. DC 2058
http://fissilematerials.org/library/doe14.pdf
Read the excerpt below taken from the text. “[…] because of their demonstrated safety and reliability, these ships have access to seaports throughout the world.” Choose the alternative that presents the words that would better translate, respectively, the ones in bold and underlined.