Let's analyse the options:
(A) Spontaneous internal bleeding and the formation of blood clots and malignancies present considerable risk during the post-heart transplant recovery process.
This option is grammatically correct and clear.
It states that three specific conditions, present risk during recovery from a heart transplant.
(let's keep this for now)
(B) The reason the post-heart transplant recovery process presents a considerably risk is because of spontaneous internal bleeding and the formation of blood clots and malignancies.
This sentence is awkwardly phrased, and the word "a" is misplaced. I think it should be "presents a considerable risk."
(eliminate)
(C) A considerable risk is presented during the post-heart transplant recovery process, where internal bleeding is spontaneous and the formation of blood clots and malignancies.
This option is awkwardly structured. There seems to be a modifier error. It implies that the recovery process is where these conditions originate, which sounds illogical.
(eliminate)
(D) The post-heart transplant recovery process presents a considerable risk due to the fact of spontaneous internal bleeding, and blood clots and malignancies are formed.
This sentence is confusing and not well constructed. It seems to imply that the recovery process itself causes these conditions, which is illogical.
Also, the usage of 'due to' is incorrect. As a test, we can replace the word 'due to' with 'caused by' and see if the sentence makes sense. In this case, it does not.
(eliminate)
(E) Spontaneous internal bleeding, along with the formation of blood clots and malignancies, are what make the post-heart transplant recovery process risky.
This sentence is grammatically incorrect because it uses "are" to refer to the singular noun phrase "Spontaneous internal bleeding, along with the formation of blood clots and malignancies". The verb should be "is" to agree with the singular subject.
(eliminate)
Option (A) seems to be the best choice. It is clear, concise, and accurately conveys the intended meaning.
I will go with (A).