Question

Dear MS. Writeacher - Thank You

1.(4). Since the previous scan, the patient has undergone surgery leaving a distorted and small right hemithorax.

I put the comma here because you could start a new sentence with The Patient .....

2.(5). The remainder of the visualized aspects of the upper abdomen were unremarkable.

Changed it to were unremarkable

Answer 1

1 = correct

The problem with #2 is that the subject (remainder) is singular, but the verb (whether it's "are" or "were") is plural. It would be better to rephrase the sentence like this:

<i>The remaining visualized aspects of the upper abdomen are unremarkable.</i> (You could also use "were" in this sentence.)

Now the subject is "aspects" (plural) and the verb agrees/matches it. Here is a link explaining the specific error in the original sentence:
http://grammar.ccc.commnet.edu/grammar/sv_agr.htm
See #8.