How can no security have an effect on houses and neighbours

Read the article titled "trans-saharan migration routes to north africa and the eu: historical roots and current trends." why do tens of thousands of sub-saharan africans try to cross the mediterranean each year? how are these refugees commonly portrayed? (site 1)

Which statement about portugal is not true? a. it granted independence to its last colony in 1975 b. it has avoided conflict with spain c. it was a leader in european world exploration in the 1400s d. its economy is changing from agricultural to industrial b. it has avoided conflict with spain

What is meant by the last line of the text? how did the maginot line serve as an example of this saying?