The correct answer is option 3, X-rays.

Cement is an essential binding material used in construction. It sets and hardens through a process called hydration, where water reacts with the cement, forming chemical bonds that give it strength and stability.

X-rays are electromagnetic radiation with high energy. They have the ability to penetrate materials, including cement, and can disrupt the process of hydration. When X-rays interact with the water-cement mixture, they can break the chemical bonds and hinder the setting action of cement.

Options 1, 2, and 4 (Ultraviolet rays, Gamma-rays, and Infra-red rays) are incorrect because they do not have the same disruptive effect on the hydration process of cement as X-rays. These types of radiation do not possess the same high energy or penetrating ability to interfere with the setting action of cement.

It is important to note that in practical applications, X-rays are not commonly used as a means to retard the setting action of cement. Other admixtures or additives are more commonly employed for this purpose.