The correct option is B Every person has good luck at some point in his life.
A proverb is a short saying that states a general truth or advice.
They're popular as they are told and retold through generations,
incorporated in books and stories that grandparents narrate to children.
Proverbs have a deeper meaning than the one you perceive at first. The
given proverb is a truth, "dog" represents man and "its day" represents good luck. Every man will get good luck or success at some point or the other in his life, hence option B gives the correct meaning of the proverb. Option A isn't true, options C and D are vague and don't explain the proverb, hence A, C and D are incorrect.