Explanation
Correct answer: B.
Choice B is the best answer. The convention being tested is the use of plural and possessive nouns. The plural possessive noun “grains’” and the plural noun “properties” correctly indicate that the simulations involved multiple snow grains and that those snow grains had several properties.
Why the other choices are wrong
Choice A
Choice A is incorrect because the context requires the plural possessive noun “grains’” and the plural noun “properties,” not the singular possessive noun “grain’s” and the plural possessive noun “properties’.”
Choice C
Choice C is incorrect because the context requires the plural noun “properties,” not the singular possessive noun “property’s.”
Choice D
Choice D is incorrect because the context requires the plural possessive noun “grains’,” not the plural noun “grains.”