Which sentence uses a comma correct way to set up an introductory phrase?

Which statement best describes the effect of the metaphor on the excerpt's meaning? o a. it compares the sloshing liquid to a river of water able to push apart the sidewalk o b. it makes the frozen crystals seem like friends to the city to contrast with what a deceitful foe they are. o c. it compares the frozen crystals to delicately lacy snowflakes having arn unexpected strength o d. it likens h20 molecules to hexagonal crystals, which are actually larger than people imagine.