Given the low efficiency of the star formation process, the initial mass of a molecular cloud fragment that formed a 2 M _$\odot$ star was probably close to: A) 10 M _$\odot$ B) 50 M _$\odot$ C) 100 M _$\odot$ D) 500 M _$\odot$ E) 1,000 M _$\odot$

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The initial mass of a molecular cloud fragment that formed a star can be estimated using the mass-luminosity relation. According to this relation, the luminosity of a star is proportional to its mass to the power of 3.5. Therefore, if we know the luminosity of the star, we can estimate its mass. The given star is a 2 MF2S2S2W1_F1F1F10 star, which corresponds to a luminosity of about 100 times that of the Sun. Using the mass-luminosity relation and assuming that the star is in the main sequence phase, we can estimate its mass to be about 10 times that of the Sun. However, the efficiency of star formation is low, typically around 10-30%. This means that only a fraction of the mass of the molecular cloud fragment will actually form a star. Therefore, the initial mass of the cloud fragment would have been higher, probably around 100 MF2S2S2W1_F1F1F10. Choices A, B, D, and E are all too high.

Given the Low Efficiency of the Star Formation Process, the Initial