because land routes were dominated by the ottoman Empire, Europeans had to -

With the Ottoman empire controlling overland trade routes, the Europeans began to search for a water route to Asia.
The Europeans were Christians and did not want to be held hostage by the Muslim Ottoman empire controlling their trade with Asia. They therefore sought another way to get to Asia and did so around Africa.
In conclusion, option B is correct.
Find out more about the Portuguese sailing around Africa at https://brainly.com/question/262829.