Question

astronaut on the space station for a prolonged time can lose bone density because

-decreased stress on the bones leads to weakening

-low sunlight in space leads to a lack of vitamin D

-it doesn't, bone never changes shape in the adult

-poor diet in space leads to lack of vitamin D and calcium

Answer 1

ANSWER - CORRECT ANSWER IS A

it is a world wide and unversal fact that the gravity on earth is one of the reasons which is responsible for the strength of the bones, along with the atmospheric pressure. what happens in space is that there is no gravity and also there is no pressure which makes the bones weak. hence correct answer is A

poor diet is not the reason, as diet is supplemented to the astraunauts which is a high level diet, also, vitamin d is constantly available in space, because of the presence of the sun, and also it is artificially being provided to them.

it has been seen and believed that the astraunauts who returns back from space, they have been seen a bit shorter in height as comparitively when they left earth , this means there is a significant change in their bone size, thus option c is also incorrect.

hence, the correct option is A