The major component/ingredient of Portland Cement is :

The correct option is D Tricalcium silicate
The important ingredients present in Portland Cement are dicalcium silicate $\left(C{a}_{2}Si{O}_4\right))$ (26%), tricalcium silicate $\left(C{a}_{3}Si{O}_5\right))$ (51%), tricalcium aluminate $\left(C{a}_{3}A{l}_2{O}_6\right))$ (11%).