A．To make a four-digit number with distinct digits，you have nine choices  of digit for the thousands place(you cannot begin with a o and call it a four．  digit number)．Next，you can use any of the other nine digits in the hundreds  place，then any of the eight remaining digits in the tens place，and any of the seven unused digits in the ones place，for a total of9×9 × 8 × 7=4．536  possibilities．The number of three-digit numbers is 9×10 × 10=900(you  can put any digit in any place except for a o in the hundreds place)． Quantity A is bigger because 4．536>900．