Which best describes a characteristic of an adiabatic process?

heat is absorbed but not released by the system.

all heat added to the system is transformed into work.

there is a gradual shift between compression and expansion of a gas.

when gas is compressed in the system, temperature remains constant.

An adiabiatic process is thermally isolated, that does not mean that the temperature does not change, what it means is that there is not exchange of heat, then any exchange of energy is as work.

You can, then, eliminate the first and the second option (because there is not abosrtion of heat).

You can also eliminate the fourth option, because when a gas is compressed abiabatically the temperature increases..

The right statement is the third: there is a gradual shift between compression and expansion of a gas. This is of the idealized forms in which an adiabatic process can occur. Nevertheless it is just an idealization or approximation. And there are other idealizations.