Which of the following values represents the proportion of all professional astronomers that is employed by a government laboratory? O one-third
three-fourths
O one fourth
one-hall

Magma forms by partial melting of upper mantle and crust. partial melt means that only a fraction of the available material forms a melt, and that the remainder stays solid. the partial melt rises because of its lower density and ascends through he crust. this is so conclusive mean the answer would be magma igneous rocks or balistic magma.