The was part of stalin’s secret police force.
a. nkvd
b. kgb
c. cia
d. swat

The correct answer is:  

a. NKVD

The People's Commissariat for Internal Affairs (NKVD) was the interior ministry of the Soviet Union. Established in 1917, it was originally tasked with conducting regular police work and managing the country's prisons and labor camps.

The duties of the OGPU (the secret police organization) were given to the NKVD in 1934, granting it a monopoly over law enforcement activities that lasted until the end of World War II. During this period, the NKVD included both ordinary public order activities, as well as secret police activities.

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.