According to today’s historical theories, native americans first migrated to the americas over years ago.
a. 500
b. 1,000
c. 5,000
d. 15,000

According to today's historical theories Native Americans first migrated to the Americas over 15,000 years ago (D).

The first settlement of the Americas began when hunter-gatherers crossed the Beringia land bridge between what is known today as Serbia and Alaska. These populations expanded south and into the Americas around 14,000 years ago.

union blockade

explanation:

the union blockade in the american civil war was a naval strategy by the united states to prevent the confederacy from trading.

the blockade was proclaimed by president abraham lincoln in april 1861, and required the monitoring of 3,500 miles (5,600 km) of atlantic and gulf coastline, including 12 major ports, notably new orleans and mobile. those blockade runners fast enough to evade the union navy could only carry a small fraction of the supplies needed. they were operated largely by british citizens, making use of neutral ports such as havana, nassau and bermuda. the union commissioned around 500 ships, which destroyed or captured about 1,500 blockade runners over the course of the war.