VLSM, summarization, and discontiguous networking are all advanced networking techniques used to efficiently allocate IP addresses, reduce routing table size, and improve network scalability. Not all protocols support these features, but some do. Let's analyze the given options to find which protocols support VLSM, summarization, and discontiguous networking.

RIPv1:
- RIPv1 (Routing Information Protocol version 1) is a classful routing protocol that does not support VLSM or summarization. It operates on the network layer and uses distance-vector algorithm.

IGRP:
- IGRP (Interior Gateway Routing Protocol) is also a classful routing protocol developed by Cisco. It does not support VLSM or summarization. Like RIPv1, it uses a distance-vector algorithm.

EIGRP:
- EIGRP (Enhanced Interior Gateway Routing Protocol) is an advanced routing protocol developed by Cisco. It supports VLSM, summarization, and discontiguous networking. EIGRP uses a hybrid routing algorithm that combines aspects of distance-vector and link-state protocols.

OSPF:
- OSPF (Open Shortest Path First) is a popular link-state routing protocol that supports VLSM, summarization, and discontiguous networking. It is an open standard protocol and is widely used in large networks.

BGP:
- BGP (Border Gateway Protocol) is an exterior gateway protocol used for routing between autonomous systems (AS). Although BGP supports summarization, it does not support VLSM or discontiguous networking.

RIPv2:
- RIPv2 (Routing Information Protocol version 2) is an enhanced version of RIPv1. It supports VLSM and summarization but does not support discontiguous networking.

Based on the above analysis, the protocols that support VLSM, summarization, and discontiguous networking are:

3) EIGRP
4) OSPF
6) RIPv2

Therefore, the correct answer is option 'C' - protocols 3, 4, and 6 (EIGRP, OSPF, and RIPv2) support VLSM, summarization, and discontiguous networking.