68. The following are exposed cards:—
1st. Two or more cards played at once.
2d. Any card dropped with its face upward on the table, even though snatched up so quickly that it cannot be named.
3d. Any card so held by a player that his partner sees any portion of its face.
4th. Any card mentioned by either adversary as being held by him or his partner.
69. A card dropped on the floor or elsewhere below the table or so held that an adversary but not the partner sees it, is not an exposed card.
70. If two or more cards are played at once by either of the declarer's adversaries, the declarer shall have the right to call any one of such cards to the current trick, and the other card or cards are exposed.
71. If, without waiting for his partner to play, either of the declarer's adversaries play or lead a winning card, as against the declarer and dummy, and continue (without waiting for his partner to play) to lead several such cards, the declarer may demand that the partner of the player in fault win, if he can, the first or any other of these tricks, and the other cards thus improperly played are exposed cards.
72. If either or both of the declarer's adversaries throw his or their cards on the table face upward, such cards are exposed and are liable to be called; but if either adversary retain his hand he cannot be forced to abandon it. Cards exposed by the declarer are not liable to be called. If the declarer say, "I have the rest," or any other words indicating that the remaining tricks or any number thereof are his, he may be required to place his cards face upward on the table. His adversaries are not liable to have any of their cards called should they thereupon expose them.
73. If a player who has rendered himself liable to have the highest or lowest of a suit called (Laws 80, 86 and 92) fail to play as directed, or if, when called on to lead one suit he lead another, having in his hand one or more cards of the suit demanded (Laws 76 and 93), or if, called upon to win or lose a trick, fail to do so when he can (Laws 71, 80 and 92), or if, when called upon not to play a suit, fail to play as directed (Laws 65 and 66), he is liable to the penalty for revoke, unless such play be corrected before the trick is turned and quitted.