The correct answer is option A: 1, 2, and 3 only.

Indian Remote Sensing (IRS) satellites are extensively used for various activities in India. Let's discuss each activity and how IRS satellites are used for them:

1. Assessment of crop productivity:
- IRS satellites provide valuable information for assessing crop productivity. They capture images of agricultural land and provide data on various vegetation indices like NDVI (Normalized Difference Vegetation Index).
- NDVI helps in monitoring the health and vigor of crops, which is crucial for assessing crop productivity and identifying areas of potential crop failure.
- This information is useful for farmers, agricultural planners, and policymakers in making informed decisions regarding agricultural practices, crop management, and food security.

2. Locating groundwater resources:
- IRS satellites play a significant role in mapping and assessing groundwater resources.
- They capture high-resolution images and provide data on land surface characteristics, such as soil moisture content and water bodies.
- By analyzing this data, scientists and hydrologists can identify potential areas of groundwater recharge, locate aquifers, and assess the availability and sustainability of groundwater resources.

3. Mineral exploration:
- IRS satellites are extensively used in mineral exploration activities.
- They provide multispectral and hyperspectral data, which helps in identifying and mapping different minerals and rock formations.
- By analyzing the spectral signatures of various minerals, geologists can locate potential mineral deposits and assess their economic viability.
- This information is crucial for mineral exploration companies and government agencies involved in mineral resource planning and development.

4. Telecommunications:
- IRS satellites are not primarily used for telecommunications purposes.
- However, they do provide support for satellite-based communication networks in remote and inaccessible areas.
- These satellites can relay communication signals and provide connectivity in regions where terrestrial communication infrastructure is limited or absent.

5. Traffic studies:
- IRS satellites are not specifically used for traffic studies.
- However, they can indirectly contribute to traffic studies by providing high-resolution satellite imagery.
- This imagery can be analyzed to monitor and analyze transportation infrastructure, road networks, and traffic patterns in urban and rural areas.

To summarize, Indian Remote Sensing (IRS) satellites are used for activities such as assessing crop productivity, locating groundwater resources, and mineral exploration. They indirectly support telecommunications and can provide valuable data for traffic studies through satellite imagery analysis. Therefore, the correct answer is option A: 1, 2, and 3 only.