Which layer of the OSI reference model is responsible for ensuring reliable end-to-end delivery of data?

The answer to this is Transport. The transport layer is the 4th layer in the OSI Model. This is responsible for the end-to-end communication between the source to the destination. This will make sure that communication will take place easily.

The transport layer is the one responsible for making sure that data will be transported from the starting point to the end point. If by any case this layer fails, this can become a problem in the long run. Take note that not all transport layers are created the same way. Most are made for the purpose mentioned earlier but there are also others that are meant to do data management tasks instead.

Transport.

A key function of the transport layer is to provide connection services for the protocols and applications that run at the levels above it. These can be categorized as either connection-oriented services or connectionless services. Some protocol suites, such as tcp/ip, provide both a connection-oriented and a connectionless transport layer protocol, to suit the needs of different applications. The transport layer is also the place in the layer stack where functions are normally included to add features to end-to-end data transport.