The correct answers are:
B. causes beach erosion and changes the coastline;
C. brings more tourists to the region;
The wave action is the main force that shapes the coastline. The water with its chemical components and sheer force manages to transform the coastal landscape, and in relatively short time (geologically speaking) it can make numerous different types of relief forms on the coast.
The wave action, and its results, in the sense of creating interesting and attractive relief forms along the coast, are a big reason for the number of tourist that will visit the particular region. The beaches are the first thing that falls on mind and what attracts tourists the most, but also there's tombola, lagoons, cliffs etc.