The enthalpy change for the reaction
Cls, graphite) + 1/2O2(g) --> CO(g) cannot be measured directly since some carbon
dioxide is always formed in the reaction.
It can be calculated using Hess's Law and the enthalpy changes of combustion of
graphite and of carbon monoxide.
C(s, graphite) + O2(g) --> CO2 AH=-394 kJmol-1
CO(g) + 1202(8) --> CO2 AH=-283 kJmol-1

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.

water and alcohols have similar properties because water molecules contain hydroxyl groups that can form hydrogen bonds with other water molecules and with alcohol molecules, and likewise alcohol molecules can form hydrogen bonds with other alcohol molecules as well as with water.

a is the correct answer