The correct answer is A.
The first thing you should do when a person is drowning is to call for more help (step 5). Answers B and D can therefore be eliminated.
According to answer A, after calling for help you should get a flotation device (step 2) and then swim to the victim (step 4).
According to answer C, after calling for help you should swim to the victim (step 4) and then get a flotation device (step 2).
Answer A must be correct, as you must get a flotation device before swimming towards the victim.
You may also have noticed:
When someone is drowning, every second is crucial. Therefore, you should only apply medical assistance (step 3) after the victim has been safely removed from the water.
You must swim to the victim (step 4) before placing your arm underneath his (step 1), before putting the flotation device between yourself and the victim (step 6), and before bringing the victim to safety (step 7).