Step 1: ASHA stands for Accredited Social Health Activist, a community health worker created under the National Rural Health Mission (NRHM) in 2005.
Step 2: The ASHA is selected from the village she serves. The norm is one ASHA per 1000 population at the village level, so she is a resident village-level volunteer who links the community to the health system.
Step 3: The other options name health facilities staffed by trained personnel. A sub-centre is the most peripheral facility (manned by an ANM and a male health worker), a Primary Health Centre is run by a medical officer, and a Community Health Centre is a 30-bedded first referral unit. The ASHA is not posted at any of these; she works in and from the village.
Step 4: The answer is option A, village level.