Use  t =  1 M2.5  to compute the life expectancy of a 0.6-solar-mass star. (A solar lifetime is approximately 10 billion years.)  yr Why might this be an underestimate if the star is fully mixed by convection? a) If the star is fully mixed its mass will be much larger than 0.6 solar masses. b) If the star is fully mixed its mass will be much smaller than 0.6 solar masses.     c) If the star is fully mixed it will

Which statement is most logical?  a Once gravity overcomes thermal pressure, nebulae cloud turns into molecular cloud. If it is cold and dense enough, molecular cloud might turn into protostar.  b If gravity is stronger than thermal pressure, nebulae cloud contracts into molecular cloud. If it is cold and dense enough, molecular cloud might turn into protostar.  c If a molecular cloud is cold and dense enough, it turns into a protostar. Once gravity overcomes thermal pressure, protostar might become molecular cloud.  d If a nebulae cloud is cold and dense enough, it turns into molecular cloud. If gravity is stronger than thermal pressure, molecular cloud might become protostar.