Which is a sentence fragment?

a.
this is the way we've always done it.

b.
can't i go with them?

c.
trevor and diane stopped by.

d.
the sun glinting off the worn glass.

Read the excerpt from the time traveler's guide to elizabethan england.simon forman, who does attend plague sufferers, is a rare exception: this is because he has himself survived the disease and believes he cannot catch it again. however, his remedy amounts to little more than avoiding eating onions and keeping warm. he has a recipe for getting rid of the plague sores that will afflict you afterward if you survive the disease; but that is a very big "if.” it seems the best advice is provided by nicholas bownd in his book medicines for the plague: "in these dangerous times god must be our only defense.”which lines best summarize the excerpt?