(1) Natural, usually six or more clubs.
The late Jim Jacoby was well known as a syndicated columnist and professional bridge player.
As such, he was a very fine declarer. This deal is from the Bermuda Bowl in Stockholm, Sweden, in 1983. The opponents were from New Zealand. Jacoby was playing with Jeff Meckstroth (Eric Rodwell had taken ill).
The contract at both tables was 4♠. Above was how Jacoby and Meckstroth got there.
The play started identically at both tables. West cashed two high clubs and switched to a heart.
Declarer won in hand, drew two rounds of trumps, ending in dummy, then ruffed dummy’s last heart. At that point, the strategies of the two South players diverged.
In one room, the New Zealand declarer simply played a diamond to the ace and another diamond to the 10, queen and king. Down one.
Jacoby had a better idea. He went to dummy with a third round of trumps and played the ♦8.
When East inserted the ♦J, Jacoby had to make a decision. He finally decided that East was more likely to have the ♦J 10 x (x) than the J-x (x). In the latter case, it would be correct to play the queen, endplaying West to lead away from the 10. After considering his play for some time, Jacoby played low. East then had the choice of continuing diamonds, picking up the suit for Jacoby, or giving a ruff-sluff by playing a heart. Either way, Jacoby had his vulnerable game and a 12-IMP pickup.
The full deal: