Deal 18
 
  3NT
OL: 5
♠ 6 4 2
9 6 4
K Q 8 3
♣ K 7 3
 
 WEST  NORTH  EAST  SOUTH
2NT
pass3NTpasspass
pass

You are East. The bidding has been as shown.
Partner led the 5, you put on the J, South won with the A.
The second trick was A, 2, 3, 5.
The third trick was J, 6, 8, 7.
South then put the ♣Q on the table.

When you have made your choice click NEXT .

5
2 6
♣ 4
♠ J 10 7 3
J 7 2
10 7 5
♣ A 9 5
 
A
A J
♣ Q
 

 
Deal 18
 
  3NT
OL: 5
♠ 6 4 2
9 6 4
K Q 8 3
♣ K 7 3
  Play the ♣A.

Does it look to you like South is trying to create an entry to dummy so he can cash the 2 winners?
That's what he wants it to look like, hoping someone holds up their ♣A.

But don't believe Declarer, believe your partner.
On the first West played the 2.
On the second he played the 6.
He has an odd number of s, obviously 3.
And South must also have a third one, so he is up to some trickery with that ♣Q.

So grab your ♣A and return partner's suit.

 Deal 19 
♠ 9 8 5
K Q 8 5 3
9 6 2
♣ J 4
♠ J 10 7 3
J 7 2
10 7 5
♣ A 9 5
  ♠ A K Q
A 10
A J 4
♣ Q 10 8 6 2