B. The time and date you read the source material.
Explanation:
Summary notes are a great technique to condense the main ideas of a text for easy and later retrieval. As such, they should be written down in one´s own words, detailing the main ideas of the text as they are relevant to one´s own work, in order to express one´s comprehension of the text. All of the factors provided in the answer above should be included in order for the summary notes to be complete; and, although the time and date of the reading is not strictly or necessarily a part of summary notes, I find it edifying to include them so that one can see, when the notes are reviewed (days, months, and even years later), what one´s mindscape was like back then in comparison to the present when the notes are reviewed.
