Recently, linking of which of the following rivers was undertaken?

1. A

   Cauvery and Tungabhadra

   Cauvery and Tungabhadra are east-flowing Peninsular rivers with their own disputes and reservoirs; a recently undertaken interlinking of this pair was not the project in the news this question uses. This option is not the key.

2. B

   Godavari and Krishna

   The Godavari–Krishna link (Pattiseema lift irrigation / Polavaram–Krishna transfer in Andhra Pradesh) was the inter-basin transfer actually taken up and inaugurated in this period, moving Godavari surplus toward the Krishna delta. That is why (b) is the official key.

3. C

   Mahanadi and Son

   Mahanadi and Son belong to different basins (Bay of Bengal vs Ganga). No such completed linking was the contemporary news item. This option is wrong.

4. D

   Narmada and Tapti

   Narmada and Tapti are parallel west-flowing rivers; their linking was not the project undertaken in the news. This option is not the key.

Summary. Official key is (b) Godavari and Krishna. Andhra Pradesh operationalised a link to divert Godavari water into the Krishna system to stabilise delta irrigation, billed as an early National Perspective Plan-style transfer. Cauvery–Tungabhadra, Mahanadi–Son and Narmada–Tapti were not that completed pairing. River-linking questions often test which pair actually moved water, not which pair exists on a map.