An isothermal process is:
(A) Slow process
(B) Quick process
(C) Very quick process
(D) Both A & B

Hint: In this question, we have to find that the isothermal process is fast or slow. To find this we check out what is an isothermal process and the effect of temperature on this process.

Complete step by step answer:
An isothermal process is thermodynamics in which the temperature of a system remains constant. The transfer of heat into or out of the system happens so slowly that thermal equilibrium is maintained. At a particular constant temperature, the change of a substance, object, or system is known as the isothermal process.
Usually, there are two phenomena under which this process can take place. If a system is in contact with a thermal reservoir from outside, then to maintain thermal equilibrium, the system slowly adjusts itself with the temperature of the reservoir through heat exchange.
An isothermal process is a process in which the temperature remains constant: $\Delta T=0$. This typically occurs when a system is in contact with an outside thermal reservoir, and the change occurs slowly enough to allow the system to continually be in thermal equilibrium with the reservoir through heat exchange.

Hence it’s a slow process. So option A is the correct answer.

Note: To understand this question we have to study the isothermal process. An isothermal process is a process that occurs under constant temperature but other parameters of the system can be changed accordingly to the situation. After understanding the isothermal process we can easily solve these types of questions.