Jack is the name of a game. It is quite popular with children. To play jacks, you will need a small ball and ten small metal objects   called jacks. The rules for this game are quite easy. To begin with, put the ten jacks on the floor or ground in front of you. Toss the ball high, pick up one jack and then catch the ball. Keep the jack in your hand and go on to pick up the other jack one at a time. You lose your turn if you do not catch the ball, or if you do not pick up a jack, or if you drop   any of the jacks from your hand. When you finish all the ten jacks, you now try to do the same thing again but with two jacks at one time. This is more difficult, of course. You lose your turn if you make any of the above three mistakes   or if you do not pick up two jacks each time. To play jacks is   _  .
difficult for boys interesting for children difficult for girls interesting for old people