**Core Concept**
KFD (Kyanasur forest disease), also known as Kyasanur Forest Disease, is a tick-borne viral hemorrhagic fever endemic to the Indian subcontinent. The disease is caused by a virus transmitted through the bite of an infected tick, primarily the Haemaphysalis spinigera species.

**Why the Correct Answer is Right**
The virus is transmitted to humans when an infected tick attaches to the skin and feeds on blood. This transmission occurs when the tick is in its nymphal stage, which is the most common stage to infect humans. The virus then multiplies within the tick and is transmitted to the human host through the tick's saliva, causing symptoms such as fever, headache, and hemorrhaging.

**Why Each Wrong Option is Incorrect**
**Option A:** Mosquitoes - Mosquitoes are vectors for various diseases such as malaria, dengue, and Zika, but they are not associated with the transmission of KFD.
**Option B:** Fleas - Fleas are vectors for diseases like plague and typhus, but they are not responsible for transmitting KFD.
**Option C:** Sandflies - Sandflies are vectors for diseases such as leishmaniasis, but they do not transmit KFD.

**Clinical Pearl / High-Yield Fact**
KFD is a zoonotic disease, meaning it can be transmitted from animals to humans. The primary reservoir of the virus is the Indian soft tick (Haemaphysalis spinigera), which is found in the forests of India.

**Correct Answer:** C.