What did the portuguese do in order to try to create a trading post empire?

In order to create a Trading Post Empire the Portuguese decided to build more than 50 trading post around the middle of the 16th century. The area chosen to accomplish this was between east Asia and west Africa. The main purpose of these trading posts was to firmly control many of the existing trading routes rather than to gain any territory. Many vessels using these waterways were forced to stop in the trading post, thus allowing Portuguese officials to collect duties and taxes.

Unfortunately, the Portuguese strategy was only half successful because they did not have a sufficient number of ships to accurately enforce the ambitious plan.

As the sea power of England and the Dutch increased, they were able to outgrow the Portuguese vessels thus, taking  control from them and assuming the new responsibilities in a better and decisive manner.    

your answer would be (b)