With geoplogy asap,

1. it’s easy for a geologist to conclude that the protolith for marble is limestone, but it’s harder when the metamorphic rock is gneiss. why is this so? why can the protolith for gneiss be either granite or shale?

2. would a schist be more likely to be formed via regional metamorphism or contact metamorphism? why? your answer should consider the causes of foliation in metamorphic rocks