Seven players, round two. P1 said "Dapp!", P2 passed, and you are P3.
Your hand
Do you call "Challenge!"?
Answer
Pass. The XIX needs three other Taroks to be a trump stop, and you hold two. Two Taroks from the XV up feel like enough, but without a trump stop this is not a hand you would claim yourself, and the bidder could hand you a Dapp that pays double.
Rule: Call Challenge with a hand you would claim yourself, a trump stop on the ladder, and pass without one. The bidder chooses whether you play it, and either way the hand pays double.