The correct answer is option 2: DHVANI.

Option 1: SHANKH. This is not the correct answer. SHANKH is not a state-of-the-art acoustic sensor-based target training system developed by the CSIR for shooters of the Indian Army.

Option 2: DHVANI. This is the correct answer. DHVANI is a state-of-the-art acoustic sensor-based target training system developed by the CSIR for shooters of the Indian Army. It uses advanced acoustic sensing technology to provide real-time feedback and analysis for shooters during training exercises. This system helps shooters improve their accuracy, precision, and target acquisition skills.

Option 3: NISHAN. This is not the correct answer. NISHAN is not a state-of-the-art acoustic sensor-based target training system developed by the CSIR for shooters of the Indian Army.

Option 4: PRAHAR. This is not the correct answer. PRAHAR is not a state-of-the-art acoustic sensor-based target training system developed by the CSIR for shooters of the Indian Army.

In conclusion, the state-of-the-art acoustic sensor-based target training system developed by the CSIR for shooters of the Indian Army is DHVANI (option 2).