While both statements A and R are true, Reason R does not directly explain why the endometrium is necessary for implantation of the blastocyst. The role of the corpus luteum and the disintegration of the endometrium is related to the menstrual cycle and the absence of pregnancy, but it doesn't directly address the role of the endometrium in blastocyst implantation. Therefore, the correct answer is that both A and R are true, but R is not the correct explanation of A.
Therefore, the correct option is (A): Both A and R are true but R is NOT the correct explanation of A.
The assertion (A) regarding the necessity of the endometrium for blastocyst implantation is accurate. The endometrium provides the essential environment for the embryo to attach and establish a connection with the maternal blood supply.
However, the reason (R) provided, which suggests that the degeneration of the corpus luteum leads to the disintegration of the endometrium, is an incorrect explanation for the requirement of the endometrium. Although the degeneration of the corpus luteum and the subsequent decline in hormone levels do contribute to the shedding of the endometrium during menstruation, they do not directly elucidate why the endometrium is necessary for blastocyst implantation.
So, the correct option is (A): Both A and R are true but R is NOT the correct explanation of A.

A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is :
The output (Y) of the given logic implementation is similar to the output of an/a …………. gate.
What is Microalbuminuria ?

In the above represented plasmid an alien piece of DNA is inserted at the EcoRI site. Which of the following strategies will be chosen to select the recombinant colonies?