Final answer:
In a scientific study investigating the effects of a new drug on patients with heart disease, the experimental group will receive the drug and the control group will receive the placebo.
Step-by-step explanation:
In a scientific study investigating the effects of a new drug on patients with heart disease, the experimental group is the group that will receive the drug. This group is labeled as (1a). The control group, labeled as (2b), is the group that will receive the placebo, which is a substance that looks like the drug but does not have any active ingredients.