Step 1: What is physisorption.
Physisorption is physical adsorption, where gas molecules stick to a surface using only weak van der Waals forces. No real chemical bond forms.
Step 2: Check the bonding option.
Option 1 says covalent or ionic bonds form. That describes chemisorption, not physisorption, so it is wrong.
Step 3: Check the temperature option.
Option 2 says it is favoured at high temperature. But physisorption gives out heat and is favoured at low temperature. Heating actually drives the gas off. So this is wrong.
Step 4: Check the reversible option.
Because the holding forces are weak, the gas can leave easily when we lower the pressure or raise the temperature. So physisorption is reversible. This looks correct.
Step 5: Check the specific option.
Option 4 says it is very specific. Physisorption is not specific at all, any gas can stick on any surface to some degree. So this is wrong.
Step 6: Final choice.
The only correct statement is that physisorption is reversible, which is option 3.
\[ \boxed{\text{It is reversible}} \]