Water could be made to boil at 105°c instead of 100°c by

a.)decreasing the external pressure
b.)adding a lot of energy to the water
c.)taking the sample to a higher altitude
d.)increasing the external pressure

Option d, Increasing the external pressure

Explanation:

Boiling point of a liquid depends upon the external pressure.

When a liquid is heated, its vapour pressure starts increasing. When its vapour pressure reaches to the value of external pressure or atmospheric pressure, then liquid start to boil and this temperature is called boiling point of the liquid.

So, if the external pressure is increased, more heat will be required to increase the vapour pressure of the liquid. More the heat required, greater will be boiling points of liquids.

Therefore, water could be made to boil at 105°C by increasing the external pressure.

i think that the answer is c