This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to heal bruises fast
Apply ice for the first 48 hours.
A bruise is formed when a fall or blow causes blood vessels to break, causing blood flow to move to the skin's surface. When you first notice a bruise, apply ice right away.

[a]. This will slow down blood flow, creating space between the bruise and the blood vessels. Put ice packs wrapped in a towel over the bruise, then place ice cubes inside the ice pack for 15-30 minutes.
[b]. Ice can help heal a bruise fast by constricting underlying blood vessels. An ice pack, a bag of frozen vegetables, or ice in a plastic bag can serve as a cold compress.
[c]. Wrap a fresh clean towel around your hands to keep them warm. Place the ice pack in the freezer for five to ten minutes.
[d]. You should apply a minimum amount for the first 48 hours, as pain can build up in the area. From the first 48 hours to the end of the healing period, do not place ice on your skin for 10 to 15 minutes at a time.
The answer is:
[b].