Solvent is more than a solute. Like salt water. Water is the solvent and salt will be the solute
It's A. volume
Pressure =

with const depends on the chosen unit of volume
I think so...
In thermal cracking, high temperatures (typically in the range of 450°C to 750°C) and pressures (up to about 70 atmospheres) are used to break the large hydrocarbons into smaller ones. Thermal cracking gives mixtures of products containing high proportions of hydrocarbons with double bonds - alkenes.