Raise fundamentals about some stuff
The 21 Demands (of Japan). In 1915 Japancame up with the odd idea of trying to make the whole of China a protectorate – a protectorate of Japan of course. The Great War started in 1914 and Japan promptly declared war on Germany, in order to take over that country's leased territory in China.
The docking of America and Solviet Spacecraft.
There's no answer choices listed, so here's the best I can do:
Secondary sources come from people who have only read or heard about an event, so there is a possibility that they don't know the full story or they will mix in lies. With a primary source, you will get the full story and the truth.
Hope I'm not too late, and I hope this helps :)