Using the process of elimination, you can see that B is pretty much the only answer that makes sense. Answer A is not the answer because if you are learning new words, it does not really improve spelling skills. C also is not the answer because building your vocabulary does not give you much knowledge about decoding anything. Answer D is also not correct. Building your vocabulary does not help you sound out words. B is correct; learning new vocabulary teaches you more descriptive ways of saying things, which can definitely help express yourself better.
