The composition of the protoplanetary disk varies with distance from the protostar due to temperature.
Starting with those closest to the protostar, place these materials in order based on where they can be found predominantly in their solid states
a. 1. Methane, Ammonia, Carbon Dioxide 2. Iron, silicates, carbon 3. Water
b. 1. Iron, silicates, carbon 2. Water 3. Methane, Ammonia, Carbon Dioxide
c. 1. Iron, silicates, carbon 2. Methane, Ammonia, Carbon Dioxide 3. Water
d. 1. Water 2. Iron, silicates, carbon 3. Methane, Ammonia, Carbon Dioxide

b) 1. Iron, silicates, carbon

   2. Water

   3. Methane, Ammonia, Carbon Dioxide.

Explanation:

Protoplanetry disk is the disk of gases and clouds of dust that rotates around the newly made star. The temperature of the protoplanetry disk actually determines the type of the planet that is to be formed. Inner part of the protoplanetry disk is closer to the sun thats why it is the hottest and denser part and composed of the materials like Iron, silicates, carbon as they have high melting points. Then comes those materials that exist in the solid form at lower temperatures such as the volatile materials like water. Ater that the protoplanetry disk is made of highly volatile materials that exists in solid from only at low coldest temperatures. So the outer part of the protoplanetry disk  is made up of the Methane, Ammonia and Carbon Dioxide.

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

it is easily magnetized.