The correct answer is B. It used literary excerpts to illustrate word usage.
Johnson used excerpts from well known books to show how different words are used which was a completely new idea, revolutionary one, since the previous dictionaries showed what the word mean and were sometimes difficult to understand.
The following are correct: B & C
B) He agrees to perform the marriage of Romeo and Juliet as soon as possible.
Text Ev:
In one respect I'll thy assistant be;
For this alliance may so happy prove
To turn your households’ rancour to pure love. (p.47)
C) He is concerned that Romeo May forget Juliet as quickly as he forgot Rosaline.
Text Ev:
Holy Saint Francis! What a change is here!
Is Rosaline, that thou didst love so dear,
So soon forsaken? Young men's love then lies
Not truly in their hearts, but in their eyes. (enotes etext p. 46)
You are describing someone in I think in 3rd person because you are using the word them.