Explanation :
Calcium belongs to the s-block of the periodic table.

• The periodic table is divided into four blocks: s-block, p-block, d-block, and f-block, based on the types of atomic orbitals that are being filled.
• s-block elements include alkali metals (group 1) and alkaline earth metals (group 2). Calcium is part of group 2, making it an alkaline earth metal. Hence, statement regarding Calcium is correct.
• Iron belongs to the d-block of the periodic table as it is a transition metal. It does not qualify for the s-block. Hence, Iron does not belong to the s-block.
• Chlorine belongs to the p-block. It is a halogen (group 17) and does not fall under the s-block. Hence, Chlorine does not belong to the s-block.
• Uranium belongs to the f-block. It is an actinide element. Therefore, it does not belong to the s-block. Hence, Uranium does not belong to the s-block.
• Hence, the correct answer is Calcium.
  
  Additional Information
• s-block Elements:
  • s-block elements consist of groups 1 and 2. These include alkali metals (like Sodium and Potassium) and alkaline earth metals (like Magnesium and Calcium).
  • The outermost electron of these elements is present in the s-orbital. For example, Calcium has the electron configuration [Ar] 4s², indicating that its valence electrons are in the s-orbital.
  • These elements generally have low ionization energy, exhibit metallic properties, and are highly reactive.
• Specific Characteristics of Calcium:
  • Calcium is a soft, silvery-white metal and is one of the most abundant elements in the Earth's crust.
  • It is an essential element for living organisms, particularly in the formation of bones and teeth in humans and animals.
  • Calcium is widely used in industries, such as in the manufacturing of cement, lime, and plaster.
• Other Elements Mentioned:
  • Iron: A transition metal found in the d-block. It is used in the production of steel and is essential for the oxygen transport in living organisms (as part of hemoglobin).
  • Chlorine: A non-metal halogen found in the p-block. It is widely used as a disinfectant and in water purification.
  • Uranium: A radioactive actinide element from the f-block. It is primarily used as fuel in nuclear reactors.