How many prisoners were held in the Camps ? What type of work did they do?

The use of forced labour first began to grow significantly in 1937, as rearmament caused labour shortages.  Following the outbreak of the Second World War, the use of labour again increased sharply.

The invasion of the Soviet Union in June 1941 further heightened demands on the war economy, and in turn, for labour. At the same time, this invasion brought thousands of potential new workers under Nazi control. These prisoners were called Ostarbeiter (eastern workers) and Fremdarbeiter (foreign workers). The Nazis deported these people to forced labour camps, where they worked to produce supplies for the increasingly strained war economy or in construction efforts.

Explanation:

c is the correct answer for this question.