Ferrite:
- Ferrite is a solid solution of carbon in iron, with a body-centered cubic crystal structure.
- It is the softest and the most ductile phase of steel.
- Cementite does not exist in lamellar form in ferrite.

Bainite:
- Bainite is a microstructure that forms in steel when it is cooled rapidly from a temperature above the upper critical temperature but below the lower critical temperature.
- It consists of ferrite and cementite phases.
- The cementite in bainite is not in lamellar form, but rather in a dispersed or globular form.

Martensite:
- Martensite is a metastable phase that forms in steel when it is rapidly cooled from a temperature above the upper critical temperature.
- It is characterized by a needle-like or lath-like structure.
- Cementite is not present in martensite, as it decomposes into ferrite and carbon during the transformation.

Pearlite:
- Pearlite is a lamellar microstructure that forms in steel when it is slowly cooled from a temperature above the upper critical temperature.
- It consists of alternating layers of ferrite and cementite.
- The cementite in pearlite is in lamellar form, with thin layers embedded in the ferrite matrix.

Conclusion:
- The correct answer is option 'D' - Pearlite.
- In the pearlite phase of steel, cementite is present in lamellar form, with alternating layers of ferrite and cementite.
- In the other phases of steel (ferrite, bainite, and martensite), cementite is either absent or present in a different form.