Which one is secondary source and which one is primary source

After the united states declared war on germany, approximately how long did it take for over a million american troops to arrive in europe? a.) two months b.) two years c.) one month d.) one year

Marine exptoration of oil uses seismic waves to locate oil in the seabed. what is a negative impact from seismic waves on the aquatic ecosystem of the ocean? a.seismic waves kill microoganisms b.seismic waves disrupts the sand and causes seafloor erosion c.seismic waves have virtually no adverse affects on marine life d.seismic waves damage the sonar that dolphins and whales use to orient themselves underwater

Who was the first french explorer in america ? a. jacques cartier b. giovanni da verrazano c. samuel de champlain d. pere jacques marquette e. louis jolliet