The cheapest mode of transport for the conveyance of bulky goods across countries is

The cheapest mode of transport for the conveyance of bulky goods across countries is water transport. This is because water transport is the most fuel-efficient mode of transport and can carry large volumes of goods at once, making it more cost-effective than other modes of transport like air, land, or pipeline. Water transport also has the advantage of being able to access many locations that are not easily accessible by land or air, making it a preferred mode of transport for bulk goods like crude oil, coal, and agricultural products. Additionally, water transport is a reliable and safe mode of transport, which makes it a popular choice for international trade.