It is absolutely essential that William ________ his study in spite of some learning difficulties.
句意： 尽管威廉在学习上遇到了困难， 但他继续学习是绝对必要的。It is essential that sb. (should) do sth.为固定句型， 意为“某人有必要做某事”。 因此，本题的正确答案为B。