Just to add to beeparoo's explanation...
The problem states that the children multiply the card's value by a number greater than that card. So for example, you had a card value "5". Now you could multiply this by any number greater than 5, say 6/7/8/9... to get a result 30/35/40/45...
But the question also mentions that the range of these multiplications is between 15 and 200. So if you had a card 3, you could multiply that by 4, but that would give you 12 (<15). So the minimum card would have to be 4 so that the min possible value is 4*5 = 20.
This leaves you with option (c) and (d) only. Now for the higher range, take the answer and plug it in to arrive at answer (c).