At sea level, the size amid the 2 alkanes lets for pentane to simmer at a lower temperature than hexane. Phenol has a higher boiling point due to hydrogen bonding High altitude would have the same order while low pressure only cuts the temperature at which a solvent boils. Boiling has to do with molecular size, the occurrence/nonappearance of hydrogen bonds, and other steric issues.
So the answer would be pentane high altitude, hexane high altitude, hexane sea level, hexanol sea level. In order of boil first to boil last. This is clarified because altitude has a better effect on vapor pressure (and hence boiling points) than inter-molecular forces.
You can conclude that the solution is probably acidic because bases rarely react with metals.
ANSWER
Both trucks will move together with speed v = 6.67 m/s
so correct answer will be
The speed of the combined vehicles is less than the initial speed of the truck.
EXPLANATION
As we know that there is no external force on the system of two trucks
So here momentum of the two trucks before collision and after collision will remain same
So here we will have

so here we will have




now we will have


so correct answer will be
The speed of the combined vehicles is less than the initial speed of the truck.