• AThe fragmentation of an IP datagram is performed only at the source of the datagram
• The fragmentation of an IP datagram is performed at any IP router which finds that the size of the datagram to be transmitted exceeds the MTU
• The reassembly of fragments is performed only at the destination of the datagram
• DThe reassembly of fragments is performed at all intermediate routers along the path from the source to the destination

In IPv4, any router along the path can fragment a datagram if the outgoing link's MTU is smaller than the datagram (B true, A false — fragmentation isn't limited to the source). Reassembly, by contrast, happens ONLY at the final destination, never at intermediate routers (C true, D false).