The proportion of dissolved substances in seawater is usually expressed in

a. parts per hundred.
b. parts per thousand.
c. parts per ten thousand.
d. parts per million.

i'm not sure if it's b or d, explain

Salutations!

The proportion of dissolved substances in seawater is usually expressed in

The proportion of dissolved substances in seawater is usually expressed in parts per thousand. Parts per thousand can also be called as salinity. Its expressed as parts per thousand because the proportion of dissolved substances in seawater is very limited.

Thus, your answer is option B.

Hope I helped :D

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.