The correct alternative to this question would be alternative C)"A secondary source summarizes large amounts of evidence."
In very simple words, Primary Sources of Information are sources of information that come from the period of the events being studied. A Nazi Military journal written by a German Soldier during WWII is a Primary Source of information.
A Secondary Source is from a period after the events that are being studied occurred. It summarizes large amounts of evidence. A Secondary Source, would be, for example, a 2018 study made by a group of historians on World War II, using as one of their references the journal mentioned in the previous example.
The reason why alternative C is correct, is that in 2018, for example, World War II has already ended, and we can examine all sorts of information that might have been classified or even unknown to a primary source. Compiling all of the available information, as well as analyzing the aftermath of the events can result in a deeper and more complete study, making second sources of information more helpful.
