**Core Concept**
Preeclampsia is a pregnancy complication characterized by **high blood pressure** and often accompanied by significant amounts of **protein in the urine**. This condition can lead to severe complications for both mother and baby if not managed properly. The underlying pathophysiology involves **endothelial dysfunction**.

**Why the Correct Answer is Right**
The correct answer involves a combination of symptoms, but primarily, **hypertension** and **proteinuria** are the hallmark diagnostic criteria for preeclampsia. **Convulsions** are associated with the severe form of preeclampsia, known as **eclampsia**. While **pedal edema** can be seen in normal pregnancies and is not specific to preeclampsia, the combination of hypertension and proteinuria is pathognomonic.

**Why Each Wrong Option is Incorrect**
**Option A:** Hypertension alone, although a key feature, does not fully capture the diagnostic criteria for preeclampsia.
**Option B:** Proteinuria alone is also insufficient as it can be present in other renal conditions.
**Option C:** Convulsions are indicative of eclampsia, a progression of preeclampsia, but not all cases of preeclampsia will have convulsions.
**Option D:** Pedal edema, while common in pregnancy, is not specific to preeclampsia.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that preeclampsia is a multisystem disorder, and its severity can be gauged by the presence of **severe hypertension** and **significant proteinuria**, with or without **symptoms** such as headache or visual disturbances.

**Correct Answer:** D. a, b, and c.