Writing question

<ol>
<li>Katarina could not be certain whether the voice she heard on the recording was her uncle or someone else who speaks with a heavy German accent.</li>
</ol>

<p>A) uncle or someone else
B) uncle or that of someone else
C) uncle's or someone else
D) uncle's or that of someone else
E) uncle's or someone else's</p>

<p>I couldn't choose between D and E. Aren't they both correct? The right answer is D. Could someone explain to me why E isn't right?</p>

<hr>

<ol>
<li>As the price of petroleum rises and concern about the environmental effects of petrochemicals mounted, the plastics industry is racing to create plastics not made from petroleum. No error</li>
</ol>

<p>The error in the sentence is mounted. Why is it "mounted"? Shouldn't is racing be changed to "has been racing"? PLEASE HELP!</p>

<p>E isn’t right because you need ‘‘or that of’’ in there. This is an example of Parallelism. I think you need ‘‘or that of’’ to make a clear reference to the voices. Sorry if my explanation is confusing :(</p>

<p>^ Right. She’s not hearing someone else on the radio (even though we may say it that way in conversation), she’s hearing the voice of someone else on the radio. “That” takes the place of “the voice.”</p>

<p>For #2, “mounted” should be changed to “mounts.” That way, all the verbs in the sentence are in the present tense: “rises,” “mounts,” “is.”</p>