The core transformer is laminated because
A. The weight of the transformer may be reduced
B. Rusting of the core may be prevented
C. The ratio of in primary and secondary may be increases
D. Energy losses due to the eddy current may be minimized

Hint: Transformers contain two coils of wire they are wrapped around a core of iron.
Transformer work by induction.
 The Induction takes place if the current flows in one conductor or one set of windings in the transformer and the magnetic field that forms around that conductor sweeps the other conductor and it induces a voltage.

Complete step by step solution:
From Faraday's law of ElectroMagnetic induction, if a conductor is subjected to alternating magnetic flux, then an E.M.F is induced in the conductor. When the conductor forms a closed path then-current is induced in that conductor.
 The core gets the alternating magnetic flux which is produced by the primary of the transformer. Hence E.M.F is induced in the core. After all the core forms a closed path current gets induced which is called Eddy currents.
The core has some resistance. So the losses are made which decreases the efficiency of the transformer. So we have to reduce this eddy current. To increase the resistance of a material we have to reduce the current.
 We know that the resistance of a material is inversely proportional to the area of the cross-section. To increase resistance, we have to decrease the area of the cross-section. Here, we are decreasing the area of cross-section by using laminated sheets in the case of the transformer, thereby increasing the resistance, thus limiting the eddy currents.
So, the answer is an option (D).

Note:
The loops of electric current are generated by the eddy current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of induction.
The eddy currents heats up the core and cause losses by distorting the main current.
when the core is a single piece then its area would be high, and hence low resistance which causes a larger current to flow increasing the losses.