In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers. Construction work began on the North Tower in August 1968, and construction on the South Tower was under way by January 1969. The original Hudson Tubes, which carried PATH trains into Hudson Terminal, remained in service during the construction process until 1971, when a new station opened. The topping out ceremony of 1 WTC (North Tower) took place on December 23, 1970, while 2 WTC's ceremony (South Tower) occurred later on July 19, 1971. The first tenants moved into the North Tower on December 15, 1970, while the South Tower started accepting tenants in January 1972. When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million. The ribbon cutting ceremony was on April 4, 1973.

See options at the end. Can we conclude that were the twin towers built at the same time?

Choices: +no; +yes;
yes