You hold Ace-4 — a soft 15, meaning the ace still counts as 11. Dealer shows 10. The correct basic-strategy play:
The beauty of soft 15 (Ace-4): you cannot bust — the ace simply drops to 1 if the card is big. Against a dealer 10 (only 21% bust chance), your current total isn't good enough to stand on, and doubling doesn't pay against a card this strong. Free shot at improving: take it.
Soft hands are where most casual players leak the most: they play them like hard totals and miss every profitable double. Learning the six soft-total rows of the chart is the fastest win-rate upgrade there is.