**Core Concept**
Sandflies are vectors of various diseases, including leishmaniasis and sandfly fever. These insects are capable of short-distance flight, but their range is limited due to their small size and relatively weak flying muscles.

**Why the Correct Answer is Right**
Sandflies can fly up to approximately 50 yards (45.72 meters) in a short duration. This short-range flight is essential for their survival, as it allows them to locate potential blood meals, mates, and suitable breeding sites. Sandflies are not capable of long-distance flight, unlike mosquitoes, which can travel several kilometers.

**Why Each Wrong Option is Incorrect**
**Option B:** 100 yards is an overestimation of sandfly flight range, which is not supported by scientific evidence.
**Option C:** 200 yards is an even greater exaggeration, as sandflies are not known to fly such distances.
**Option D:** 300 yards is an unrealistic expectation, given the physical limitations of sandflies.

**Clinical Pearl / High-Yield Fact**
It's essential to note that sandflies are most active during twilight hours and are often found in areas with high humidity and temperatures between 20°C and 30°C. This knowledge can aid in vector control measures and disease prevention strategies.

**✓ Correct Answer: A. 50 yards**