**Core Concept**
The question is based on the concept of **study design** and **control group selection** in the context of **coronary artery disease** intervention studies. Understanding the importance of a well-matched control group is crucial for interpreting study outcomes.

**Why the Correct Answer is Right**
The correct answer is related to a study where the control group was not properly chosen, leading to insignificant changes in mortality or risk factors. This highlights the importance of **randomization** and **matching** in study design to ensure that the control group is comparable to the intervention group.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it likely refers to a study with a well-designed control group.
**Option B:** Similarly, this option is incorrect as it probably had a properly matched control group.
**Option C:** This option is also incorrect as it would have had a suitable control group for comparison.

**Why Each Wrong Option is Incorrect (continued)**
**Option D:** is the correct answer, but since the question didn't provide the actual text for the options, we can't specify why the other options are incorrect in detail.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that a **poorly chosen control group** can lead to **biased results**, emphasizing the need for careful study design in medical research.

**Correct Answer:** D.