Because he had not experienced any symptoms until adulthood

Hey ardz24,

There are two issues with E.

The main issue is with tense: we start in past tense (he did not experience any symptoms until adulthood) and then switch to past perfect (and had been affected by facial paralysis early on in the course of his illness ). Since past perfect is the past of the past, this implies that the facial paralysis happened BEFORE he experienced any symptoms ... but that doesn't make any sense because facial paralysis IS a symptom. We know that the facial paralysis happened in his adulthood, so we should start with past perfect (he had not experienced any symptoms until adulthood) and then end with simple past (and was affected by facial paralysis early on in the course of his illness).

The other issue is the use of "since" to mean "because". "Since" CAN mean "because", but it can also refer to time. It is preferred to simply use "because" to make the meaning as clear as possible. This is a minor, stylistic issue, so I wouldn't bank on it too much on the test when there are bigger grammatical issues (like tense) at play.