Final answer:
The most appropriate reference system for approximating the mass of a nebula is thousands of times the mass of our sun, as nebulae contain material to form many stars, each of which can be comparable to the sun's mass.
Step-by-step explanation:
The question asks about approximating the mass of nebulae and which reference system is MOST appropriate. Nebulae can vary widely in mass, but they are typically very massive structures consisting of gas and dust in space. Considering options A) half the mass of our earth, B)1/10th the mass of the sun, C) thousands of times the mass of our earth, and D) thousands of times the mass of our sun, the most appropriate reference system is D) thousands of times the mass of our sun. This is because nebulae are birthplaces of stars and can contain enough material to form hundreds or even thousands of stars, with each star potentially comparable in mass to our sun.
For instance, the mass of the Milky Way Galaxy, which encompasses many nebulae and stars, is about 100 billion times the mass of our Sun. This indicates that individual nebulae within the galaxy also possess masses that can be much greater than that of the Sun or Earth. Therefore, comparing the mass of a typical nebula to Earth's mass significantly underestimates it.