Piggyback is a form of intermodal transportation that primarily involves the following two transport modes:
1. truck and rail
2. water and pipeline
3. air and water
4. air and rail

1) truck and rail

Explanation:

Piggyback is defined as the transportation service in which goods or products are transmitted from one place to other through carrying it on the back of something. It is referred as the combined transportation service.

Truck and rail are the medium of transport that are involved in piggyback transportation .This medium consist of truck on the train which depicts railroad truck for carrying goods in containers. This method is cheap transport service.

Other options are incorrect because water , air and pipeline are not the modes of carrying goof for transportation. Thus, the correct option is option(1).

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