river bed (river beds plural) , riverbed A river bed is the ground which a river flows over. n-count. up-river, upriver. Something that is moving up-river is moving towards the source of a river, from a point down the river.
In economics, the term trade-off is often expressed as an opportunity cost, which is the most preferred possible alternative. A trade-off involves a sacrifice that must be made to get a certain product or experience. A person gives up the opportunity to buy 'good B,' because they want to buy 'good A' instead.
Tertiary economic activities are the service industry.Trade is tertiary activity in which transportation is very important via air route,land route.on economic activity is just the opposite. Activity in the economy that does not affect GDP. My understanding is that it is essentially unpaid work. Like if you clean your house or mow your lawn and do not get paid for your time/efforts.