What is the temperature of the substance when it is in its standard state?

The temperature of the substance at standard state is 25 °C.

Explanation

The standard state is the condition defined by the chemistry society to refer the temperature and pressure of any state of matter.

It is fixed for all the three states of matter. The standard state acts as reference for the change in temperature and pressure.

Generally, room temperature and pressure in a room without any external force is termed as standard conditions.

The parameters and properties for chemical reactions and elements are determined with respect to standard conditions for acting as a reference state.

So it is known that the room temperature or standard temperature is 25 °C and pressure is 1 bar.

the answer is definitely c.

the answer to your question is c