The correct option is
A Save for rainy days.
In order to find out the moral of the story, let's read the passage. The last sentence of the passage explains us the moral - "Think of keeping something for the rainy days." The moral explains that we must save things for the difficult times.
Option A - The ants tell the cricket to save something for the rainy days as he might feel hungry later as well and if he finishes everything now, there will be nothing left for later. However, the ants never ask the cricket to wait for the rainy season. Hence, option A is incorrect.
Option C - The moral of the story is that the cricket should save some grains for the rainy days. 'Rainy days can come any day' isn't the moral of the story. Hence option C is incorrect.
Option B - The ants tell the cricket to think of keeping something for the rainy days, which means, toreservesomething, in this case, grainsforuseinatimeorperiodofunforeseendifficulty,trouble,or need. Hence option B is correct.
Option D is incorrect, as option B is the correct answer.