Which agency describes sentinel events as ones in which injuries have occurred in an ambulatory-care setting?

The cells that are believed to mediate the destructive basal cell changes seen microscopically in lichen planus are:

a. Plasma cells b. T lymphocytes c. B lymphocytes d. Langerhans cells e. Keratinocytes

The physician ordered 50 mL of 1:20 W/V solution, diluted to 1000 mL. What is the ratio strength of W/V?

1:200 1:300 1:400 1:500