1) The Russian Revolution in 1917 resulted in the overthrow of the monarchy and the establishment of a communist government under Vladimir Lenin.

2) The French Revolution, which began in 1789, marked a major turning point in European history, leading to the overthrow of the monarchy and the rise of republicanism.

3) The Earth's core is primarily composed of iron and nickel and is as hot as the surface of the sun.

4) Cows have best friends and can become stressed if they are separated.