What type of reaction is   3ca(oh)2 + al2(so4)3 = 3caso4 + 2al(oh)3 combustion, synthesis, decomposition, single displacement, double displacement, or acid-base neutralization

Answer is: Double Displacement.
Combustion is reaction with oxygen.
Synthesis is reaction of two or more substances combining to make a more complex substance. 
Decomposition is reaction where one substance is broken down into two or more simpler substances. 
Single Displacement is reaction where  neutral element metal or nonmetal become an ion as it replaces another ion in a compound. 
Double displacement reactions (more reactive metals displace metals with lower reactivity).
Neutralizationis is reaction in which an acid and a base react quantitatively with each other.

You would be correct, boiling water does disinfect contamination.    the property of disinfecting means to kill  germs, bacteria and other pathogens or contamination  that might cause an infection or cause a person to become sickly. a couple methods of disinfecting are using soap, other cleaning supplies or by simply "boiling" the contaminate.  the reason why boiling water disinfects certain attributes is because some cells cannot survive the heat and pressure.

Here is the link to the all information u need i mean answer key