A--The main idea of the passage is no goods can be brought into England or into any part of the English empire unless it is on an English owned ship. The document is restricting trade within the British empire to only trading within the empire.
B--One restrictions is that goods from England and the English plantations must travel on ships owned by the English or an English plantation owner.
C--A negative impact in a closed economic system is the inability to grow the economic system by trading with other countries. They also would not be able to bring in any other goods directly from any country except England.
This document is part of the Navigation Acts imposed on the colonies in the mid-1600s. The goal of the acts for England was to restrict the trade of their colonies to only benefit England. They did not want the colonies trading with the Dutch or the French which they had begun being in close proximity to the other countries' colonies in the Americas.