Explain the Completely Randomized Design

Explain the Completely Randomized Design
-A drug company wanted to test a new depression medication. The researchers found 700 adults aged 25-35 and randomly assigned them to two groups. The first group received the new drug, while the second received a placebo. After one month of treatment, the percentage of each group whose depression symptoms decreased was recorded and compared. How many levels does the treatment in this experiment have

A) 2 (medication or placebo)
B) 700 (number of respondents)
C) 1 (months of treatment)
D) 10 (age span of respondents)