Which of the following is a common property or characteristic of an acid?
slippery feel

bitter taste

increases the hydroxide ion concentration in solution

reacts with active metals to produce hydrogen gas

The characteristic that is common to acids are that they can react with active metals to produce hydrogen gas.

REACTS WITH ACTIVE METALS TO PRODUCE HYDROGEN GAS is a common property or characteristic of an acid.

Here are the characteristics of an acid.
pH < 7
Sour taste
Reacts with a metal to form hydrogen gas
Increases the H+ concentration in water
Donates H+ ions
Turns blue litmus indicator red

The number of protons in a nucleus

They are like other investigations? say there was a murder u have to do blood test and finger prints which run through a lab.