You chose to DOUBLE which on the 1 Level would be interpreted as a Takeout Double. This is correct. You have a 4 card suit in each of the unbid suits, and more than 13 points, and you are asking your partner to choose what suit to have as trump.

So the bidding so far as gone: West, 1 Heart, North, Double, and now East will No Bid.

Here is South's hand.

Spades          K,9,7,6,5
Hearts           Q,J
Diamonds      10,9,3
Clubs            A,J,6

The Response bid to a Takeout double is forced if there is not an intervening bid, so South does not have the option of saying No Bid. Even if he had no points at all, he would be expected to bid. However, he has a pretty nice hand.

38. What should South bid on this hand?

a. 1 Spade
b. 1 No Trump
c. 2 Spades