The coordinating conjuctions in English are just three "and, or, but". 'And' is used to add information, 'or' to indicate alternatives, and 'but' to express contrast. These conjuctions link only units of the same level/ status, for example independent clauses.
1° sentence: Carlos put his books in his backpack, and he walked to the library. Here 'and' is appropiate because you need to add information.
2° sentence: My sister loves dogs but my brother prefers cats. 'But' is the correct one to indicate contrast between the two people's preferences.
3° sentence: Dad will make spaghetti for dinner or he will take us out for pizza. 'Or' is the correct one since the independent sentences signal alternatives
your poem has emotions in it, it has your love in it. it has a good beat to sing, it is sang in a beautiful melody. and your describing of girl is beautiful.
The best option is D studied. This word denotes a measured, even-handed approach to the issue. So, it should be :Current immigration policy must be studied before new proposals can be made.