D. parallel structure just means that all of your verbs in the comma series line up in regards to tenses, here. in choice D, it's "BE friendly," "INTRODUCE yourself," and "SMILE." these are all present tense verbs.
the rest of the choices don't match--"exercise" and "stretching" are two different verb forms in choice A, "to go to the library" is the odd one out in choice B, ane "to build" doesn't match with the "-ing" verbs in choice C.
Because it was too loud or because it didn’t have space
<span>My sister applied on Tuesday to a graduate school in England.As a correction I would say that "to a graduate school in England" acts as an adverb as it explains where she applied to ie modifies the verb "applied".</span>
The defining moment in Greek history is the Persian Wars.
Hope this helps !
Photon