86.the days are short,___ it is now December. a.because b.for c.goes d.want Please talk about the difference between "because for" and "because for"

86.the days are short,___ it is now December. a.because b.for c.goes d.want Please talk about the difference between "because for" and "because for"

The answer is: B
Be cause is a necessary cause and effect; for is a supplementary explanation to the facts mentioned above