Sentence Correction

Clark and Florence Wallace, a husband-and-wife medical team, worked steadily and efficiently through the night, but sipping their coffee the next morning, she noticed that he seemed disoriented.
(A) sipping their coffee the next morning, she noticed that he seemed disoriented
(B) sipping their coffee the next morning, he seemed to be disoriented, she noticed
(C) as they sipped their coffee the next morning, she noticed that he seemed disoriented
(D) as they were sipping their coffee the next morning, he seemed, she noticed, disoriented
(E) he seemed disoriented, she noticed, sipping their coffee the next morning

OA: C

Ashujain wrote:Clark and Florence Wallace, a husband-and-wife medical team, worked steadily and efficiently through the night, but sipping their coffee the next morning, she noticed that he seemed disoriented.
(A) sipping their coffee the next morning, she noticed that he seemed disoriented
(B) sipping their coffee the next morning, he seemed to be disoriented, she noticed
(C) as they sipped their coffee the next morning, she noticed that he seemed disoriented
(D) as they were sipping their coffee the next morning, he seemed, she noticed, disoriented
(E) he seemed disoriented, she noticed, sipping their coffee the next morning

OA: C

(A) "sipping their coffee the next morning, she..." - their indicates the sentence talks about both people, but the comma is followed by "she"
(B) incorrect for the same reason as (A)
(C) correct, in simple past tense form.
(D) sounds awkward to me, and more complex than (C), but I'm not sure I see anything inherently wrong with it.
(E) the subject is "he", yet we're referring to "their coffee", makes it seem like he was sipping both of their coffees.