In 1977 the total dollar value of Washington's exports and imports or two-way trade was 10.4 billion dollars, whereas in 2007 the state's two-way trade was 164 billion dollars. Since 1977 there have been several major improvements to Washington's conduct of two-way trade.

International trade has flourished because Washington has excellent seaports, river ports, and airports. There has been a concerted effort to improve, expand, and modernize the state's port facilities. The commitment of two of the world's best natural seaports, Seattle and Tacoma, to become world-class container ports was instrumental in the explosive growth of domestic and international trade in Washington. This growth was based on the improvement in the transportation system and port facilities to handle large volumes of bulk cargo, general cargo, and containers. This was a joint effort of the air, rail, and trucking industries to move commodities to and from port facilities.

International trade has also grown because of the more productive and diversified Washington economy.

According to the text, why has trade grown in Washington state? Check all that apply.

All ports have become more advanced.
Two seaports can handle big bulk ships.
Dozens of new bridges were built across the state.
Air, rail, and truck industries work in coordination.
River ports have become the state’s most important ports.