Which of the following is a primary source?

D. a love letter written to John Adams from Abigail Adams.

Explanation:

When you are conducting research, you will need to use a variety of sources to obtain information on the topic you are researching. These sources will be divided in primary and secondary sources. Primary sources are those that were created at the same time as the event you are studying. They are created by people who had a direct connection with the event, and are first-hand accounts of it. An example would be this love letter.

b. major john c. frémont led a rebellion called the bear flag revolt.

explanation:

during the bear flag revolt, from june to july 1846, a small group of american settlers in california rebelled against the mexican government and proclaimed california an independent republic. the republic was short-lived because soon after the bear flag was raised, the u.s. military began occupying california, which went on to join the union in 1850. the bear flag became the official state flag in 1911.