a) Education reduces poverty in a number of ways.
A topic sentence tells what the main idea of the paragraph is about. This paragraph is all about how Education can help reduce poverty. It shows that an education in a technical or vocational area can also help reduce poverty.
Option B is not a good choice because it only speaks about skills being relevant, it says nothing about education which is the main focus of the paragraph. Option C does speak about education but it's not clear why or for what. Option D is also too vague for a topic sentence since it doesn't say what skills or why one might want to acquire them.