(1) Space flights to other planets have long been a fixture of science fiction, and in 2017 the fiction appeared to come closer to reality when the National Aeronautics and Space Administration (NASA) announced it was prioritizing eventual piloted missions to Mars and other planets. (2) It may be too soon to start planning your Martian vacation, however: there are good reasons to doubt that humans will be able to undertake long-distance space flights.
(3) For example, the body begins to lose muscle mass and bone density in low-gravity environments because the pressure of Earth’s atmosphere is removed. (4) Astronauts struggle to walk after returning from a six-month space mission; the effects of a three-year flight and a stay on Mars would be far greater. (5) Similarly, humans have a natural cycle of wakefulness and sleep attuned to daytime and nighttime on Earth. (6) Anyone who has experienced jet lag can attest to the mental and physical effects of disrupting this cycle, but we can only imagine the consequences of disrupting it for years on end.
(7) It remains to be seen whether these problems can be diminished enough for long space voyages, and it is true that monitoring, exercise, and technological fixes like sunlight-simulating LED lights have shown promise. (8) Other issues may be more troublesome. (9) Space missions are stressful, requiring long hours of repetitive activity performed in small, cramped spaces. (10) The stress lowers immune response even as outer space conditions cause microbes in astronauts’ bodies to mutate, potentially resulting in dangerous diseases. (11) Cosmic rays pose another health concern: a 2018 study from Georgetown University Medical Center found that prolonged exposure to cosmic radiation could lead to stomach and colon cancers. (12) Unless scientists can develop effective means of fighting these health risks, long-distance space travel may be too dangerous.
(13) With NASA’s attention directed to the problems of long space missions, it is certainly possible that other nations will invest in similar research. (14) But it is also possible that further research will turn up new problems that have not even been identified yet.
which version of the underlined word best conveys the writer's perspective on long space missions?
"with NASA's attention directed to the problems of long space missions, it is certain that scientists will come up with creative solutions to the elevated risks to human well-being in space much as they have addressed dangers associated with shorter missions"
А. (as it is now)
B. likely
C. possible
D assured
E. inconceivable
