**Core Concept**
The underlying principle being tested is the management of thrombocytosis, which is an elevated platelet count above the normal range. A platelet count of 8,00,000/cu.mm is within the normal range for most laboratories. **Thrombocytosis** can be primary or secondary, but in this case, the count is not elevated.

**Why the Correct Answer is Right**
Since the platelet count is within the normal range, no specific intervention for thrombocytosis is required. The management would focus on monitoring and possibly investigating the cause if the count was significantly elevated. However, given the count is 8,00,000/cu.mm, which is typically considered within the normal range, the approach would be more about surveillance rather than active treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** Without knowing the specific option, generally, any immediate pharmacological intervention would be unnecessary given the normal platelet count.
**Option B:** Similarly, without specifics, if this option suggests an invasive or immediate diagnostic procedure, it would be inappropriate without other clinical indications.
**Option C:** If this option implies a watchful waiting approach, it might seem reasonable, but without knowing the exact wording, it's hard to judge its appropriateness directly.
**Option D:** If suggesting an urgent or specific treatment, it would be incorrect due to the normal platelet count.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that a normal platelet count ranges approximately from 1,50,000 to 4,50,000/cu.mm, but this can vary slightly by laboratory. Counts slightly above this range, like 8,00,000/cu.mm, are often not immediately concerning and would typically not prompt urgent action without other clinical signs or symptoms.

**Correct Answer:** D. No action required, Platelet count is within normal limits.