Question #N1076

The main purpose of the study was to examine the effects of a new drug on the body’s immune system. Researchers recruited volunteers for the study, who were randomly assigned to either a treatment group or a control group. The volunteers in the treatment group received the new drug, while the volunteers in the control group received a placebo. The researchers then monitored the volunteers for a period of six months, measuring various immune system parameters. At the end of the study, the researchers found that the volunteers in the treatment group had a significantly lower incidence of infection than the volunteers in the control group.

Which choice best combines the sentences at the underlined portion to create a grammatically correct and stylistically effective sentence?
A. The volunteers in the treatment group received the new drug, while the volunteers in the control group received a placebo, and then they monitored the volunteers for a period of six months, measuring various immune system parameters.
B. The volunteers in the treatment group received the new drug, while the volunteers in the control group received a placebo; the researchers then monitored the volunteers for a period of six months, measuring various immune system parameters.
C. The volunteers in the treatment group received the new drug, while the volunteers in the control group received a placebo, the researchers then monitored the volunteers for a period of six months, measuring various immune system parameters.
D. The volunteers in the treatment group received the new drug, while the volunteers in the control group received a placebo; the researchers then monitored the volunteers for a period of six months, measuring various immune system parameters.