The discovery of the remains of a dockyard at Lothal prove that the people of Indus valley had- (a) international trade relations.
(b) expertise in ship building,
(c) an organised naval force.
(d) flourishing trade within India.

(a) international trade relations.

Explanation:

The discovery of the remains of a dockyard at Lothal prove that the people of Indus valley had "international trade relations."

The remains of the dockyard at Lothal were discovered in 1954. Following the scientific analysis of the Archeological Survey of India, and later discovery of foraminifera (marine microfossils) and salt by the National Institute of Oceanography, Goa, it was concluded that Lothal was a significant and prosperous trade centre in olden ages. And the trading activities involved international partners including the west Asia and Africa.